drafts: css-fonts/Fonts.html@77d3edf17f8c (annotated)

css-fonts/Fonts.html@77d3edf17f8c (annotated)

css-fonts/Fonts.html

Mon, 26 Aug 2013 16:14:56 +0900

author: John Daggett <jdaggett@mozilla.com>
date: Mon, 26 Aug 2013 16:14:56 +0900
changeset 8930: 77d3edf17f8c
parent 8927: 9c4ae1da9e9a
child 8957: b3ad55a4d7fc
permissions: -rw-r--r--

[css3-fonts] revise description of font-size-adjust to prevent confusion

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
 "http://www.w3.org/TR/html4/strict.dtd">
 <html lang=en>
  <head><meta content="text/html;charset=utf-8" http-equiv=Content-Type>
   <title>CSS Fonts Module Level 3</title>
   <!--
       FIXME when publishing: copy the current default.css and link to
       "default.css" rather than "../default.css"
    -->
   <link href="../default.css" rel=stylesheet type="text/css">
   <link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">
   <!-- I'm just experimenting here, don't get your bee in a bonnet -->
   <script src="http://use.typekit.com/xon2bky.js"
   type="text/javascript"></script>
   <script type="text/javascript">try{Typekit.load();}catch(e){}</script>
   <style type="text/css">
   body, th, td, h1, h2, h3, h4, h5, h6 {
     font-family: "myriad-pro", sans-serif !important;
   }
   body {
     padding: 2em 70px 2em 70px;
   }
   p + p, p.mtb {
     margin-top: 0.8em;
     text-indent: 0px;
   }
   #bolderlighter {
     width: 40%;
   }
   #bolderlighter th {
     text-align: center;
   }
   #fontformats td, #eventhandlers td, #fontformats th, #eventhandlers th {
     padding-right: 2em;
     text-align: left;
   }
   dd {
     margin-bottom: 1em;
   }
   #authors dd {
     margin-bottom: 0;
   }
   #fontstylematchingalg {
     list-style-type: lower-alpha;
   }
   #fontmatchingalg ul, #fontmatchingalg ol {
     margin-top: 0.8em;
   }
   #fontmatchingalg li + li {
     margin-top: 0.8em;
   }
   div.example {
     padding: 1em;
     margin-top: 1em;
   }
   div.example + div.example {
     margin-top: 2em;
   }
   div.figure {
     page-break-inside: avoid;
   }
   pre.prod { white-space: pre-wrap; margin: 1em 0 1em 2em }
   div.featex {
     width: 700px;
   }
   div.featex img {
     margin: auto;
     display: block;
   }
   span.tag {
     font-family: monospace;
     font-size: 120%;
   }
   ol ol {
     list-style-type: lower-alpha;
   }
   .idl-code {
     font-weight: bold;
     color: #c50;
   }
   </style>
   <link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
   type="text/css">
   <script defer=defer
   src="http://test.csswg.org/harness/annotate.js#CSS3-FONTS_DEV"
   type="text/javascript"></script>
  <body>
   <div class=head> <!--begin-logo-->
    <p><a href="http://www.w3.org/"><img alt=W3C height=48
     src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->
    <h1>CSS Fonts Module Level 3</h1>
    <h2 class="no-num no-toc" id=editors-draft-26-august-2013>Editor's Draft
 August 2013</h2>
    <dl id=authors>
     <dt>This version:
     <dd><a
      href="http://dev.w3.org/csswg/css-fonts/">http://dev.w3.org/csswg/css-fonts/</a>
      <!-- <dd><a href="http://www.w3.org/TR/2013/ED-css-fonts-3-20130826/">http://www.w3.org/TR/2013/ED-css-fonts-3-20130826/</a>  -->
     <dt>Latest version:
     <dd><a
      href="http://www.w3.org/TR/css-fonts-3/">http://www.w3.org/TR/css-fonts-3/</a>
     <dt>Latest editor's draft:
     <dd><a
      href="http://dev.w3.org/csswg/css-fonts/">http://dev.w3.org/csswg/css-fonts/</a>
      (<a
      href="https://dvcs.w3.org/hg/csswg/log/tip/css-fonts/Fonts.html">change
      log</a>)
     <dt>Previous version:
     <dd><a
      href="http://www.w3.org/TR/2013/WD-css-fonts-3-20130711/">http://www.w3.org/TR/2013/WD-css-fonts-3-20130711/</a>
     <dt>Issues List:
     <dd><a href="http://www.w3.org/Style/CSS/Tracker/products/18">CSS3 Fonts
      issues in Tracker</a>
     <dd><a
      href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&amp;product=CSS&amp;component=Fonts&amp;bug_status=NEW&amp;bug_status=ASSIGNED&amp;bug_status=REOPENED">CSS3
      Fonts issues in Bugzilla</a>
     <dt>Discussion:
     <dd><a
      href="mailto:www-style@w3.org?subject=%5Bcss-fonts%5D%20feedback">www-style@w3.org</a>
      with subject line “<kbd>[css-fonts] <var>… message topic
      …</var></kbd>” (<a
      href="http://lists.w3.org/Archives/Public/www-style/"
      rel=discussion>archives</a>)
     <dt>Editor:
     <dd><a href="mailto:jdaggett@mozilla.com">John Daggett (Mozilla)</a>
    </dl>
    <!--begin-copyright-->
    <p class=copyright><a
     href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
     rel=license>Copyright</a> © 2013 <a href="http://www.w3.org/"><abbr
     title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a
     href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of
     Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr
     title="European Research Consortium for Informatics and
     Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>,
     <a href="http://ev.buaa.edu.cn/">Beihang</a>), All Rights Reserved. W3C
     <a
     href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
     <a
     href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
     and <a
     href="http://www.w3.org/Consortium/Legal/copyright-documents">document
     use</a> rules apply.</p>
    <!--end-copyright-->
    <hr title="Separator for header">
   </div>
   <h2 class="no-num no-toc" id=abstract>Abstract</h2>
   <p>This CSS3 module describes how font properties are specified and how
    font resources are loaded dynamically. The contents of this specification
    are a consolidation of content previously divided into <a
    href="http://www.w3.org/TR/2002/WD-css3-fonts-20020802/">CSS3 Fonts</a>
    and <a href="http://www.w3.org/TR/2002/WD-css3-webfonts-20020802/">CSS3
    Web Fonts</a> modules. The description of font load events was moved into
    the <a href="http://dev.w3.org/csswg/css-font-load-events/">CSS3 Font Load
    Events</a> module.
   <h2 class="no-num no-toc" id=status>Status of this document</h2>
   <!--begin-status-->
   <p>This is a public copy of the editors' draft. It is provided for
    discussion only and may change at any moment. Its publication here does
    not imply endorsement of its contents by W3C. Don't cite this document
    other than as work in progress.
   <p>The (<a
    href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
    mailing list <a
    href="mailto:www-style@w3.org?Subject=%5Bcss3-fonts%5D%20PUT%20SUBJECT%20HERE">
    www-style@w3.org</a> (see <a
    href="http://www.w3.org/Mail/Request">instructions</a>) is preferred for
    discussion of this specification. When sending e-mail, please put the text
    “css3-fonts” in the subject, preferably like this:
    “[<!---->css3-fonts<!---->] <em>…summary of comment…</em>”
   <p>This document was produced by the <a
    href="http://www.w3.org/Style/CSS/members">CSS Working Group</a> (part of
    the <a href="http://www.w3.org/Style/">Style Activity</a>).
   <p>This document was produced by a group operating under the <a
    href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February
 W3C Patent Policy</a>. W3C maintains a <a
    href="http://www.w3.org/2004/01/pp-impl/32061/status"
    rel=disclosure>public list of any patent disclosures</a> made in
    connection with the deliverables of the group; that page also includes
    instructions for disclosing a patent. An individual who has actual
    knowledge of a patent which the individual believes contains <a
    href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
    Claim(s)</a> must disclose the information in accordance with <a
    href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
 of the W3C Patent Policy</a>.</p>
   <!--end-status-->
   <h3 class="no-num no-toc" id=atrisk>Features at risk</h3>
   <p>The following features are at risk and may be removed when exiting CR:
   <ul>
    <li>fallback handling for text decoration in superscript/subscript variant
     glyphs (‘<a href="#propdef-font-variant-position"><code
     class=property>font-variant-position</code></a>’)
    <li>‘<a href="#propdef-font-language-override"><code
     class=property>font-language-override</code></a>’ property
   </ul>
   <!--
 <p>This draft is a <strong>Last Call Working Draft</strong>.
 Please send comments to the
 <a href="http://lists.w3.org/Archives/Public/www-style/">www-style mailing list</a>
 as described above.  The <strong>deadline for comments</strong>
 is six weeks after the date of publication in the header, 22 August 2013.</p>
 -->
   <h2 class="no-num no-toc" id=contents>Table of contents</h2>
   <!--begin-toc-->
   <ul class=toc>
    <li><a href="#introduction"><span class=secno>1 </span>Introduction</a>
    <li><a href="#typography-background"><span class=secno>2 </span>Typography
     Background</a>
    <li><a href="#basic-font-props"><span class=secno>3 </span>Basic Font
     Properties</a>
     <ul class=toc>
      <li><a href="#font-family-prop"><span class=secno>3.1 </span>Font
       family: the font-family property</a>
       <ul class=toc>
        <li><a href="#generic-font-families"><span class=secno>3.1.1
         </span>Generic font families</a>
       </ul>
      <li><a href="#font-weight-prop"><span class=secno>3.2 </span>Font
       weight: the font-weight property</a>
      <li><a href="#font-stretch-prop"><span class=secno>3.3 </span>Font
       width: the font-stretch property</a>
      <li><a href="#font-style-prop"><span class=secno>3.4 </span>Font style:
       the font-style property</a>
      <li><a href="#font-size-prop"><span class=secno>3.5 </span>Font size:
       the font-size property</a>
      <li><a href="#font-size-adjust-prop"><span class=secno>3.6
       </span>Relative sizing: the font-size-adjust property</a>
      <li><a href="#font-prop"><span class=secno>3.7 </span>Shorthand font
       property: the font property</a>
      <li><a href="#font-synthesis-prop"><span class=secno>3.8
       </span>Controlling synthetic faces: the font-synthesis property</a>
     </ul>
    <li><a href="#font-resources"><span class=secno>4 </span>Font
     Resources</a>
     <ul class=toc>
      <li><a href="#font-face-rule"><span class=secno>4.1 </span>The
       <code>@font-face</code> rule</a>
      <li><a href="#font-family-desc"><span class=secno>4.2 </span>Font
       family: the font-family descriptor</a>
      <li><a href="#src-desc"><span class=secno>4.3 </span>Font reference: the
       src descriptor</a>
      <li><a href="#font-prop-desc"><span class=secno>4.4 </span>Font property
       descriptors: the font-style, font-weight, font-stretch descriptors</a>
      <li><a href="#unicode-range-desc"><span class=secno>4.5 </span>Character
       range: the unicode-range descriptor</a>
      <li><a href="#composite-fonts"><span class=secno>4.6 </span>Using
       character ranges to define composite fonts</a>
      <li><a href="#font-rend-desc"><span class=secno>4.7 </span>Font
       features: the font-variant and font-feature-settings descriptors</a>
      <li><a href="#font-face-loading"><span class=secno>4.8 </span>Font
       loading guidelines</a>
      <li><a href="#font-fetching-requirements"><span class=secno>4.9
       </span>Font fetching requirements</a>
     </ul>
    <li><a href="#font-matching-algorithm"><span class=secno>5 </span>Font
     Matching Algorithm</a>
     <ul class=toc>
      <li><a href="#font-family-casing"><span class=secno>5.1 </span>Case
       sensitivity of font family names</a>
      <li><a href="#font-style-matching"><span class=secno>5.2 </span>Matching
       font styles</a>
      <li><a href="#cluster-matching"><span class=secno>5.3 </span>Cluster
       matching</a>
      <li><a href="#char-handling-issues"><span class=secno>5.4
       </span>Character handling issues</a>
      <li><a href="#font-matching-changes"><span class=secno>5.5 </span>Font
       matching changes since CSS 2.1</a>
      <li><a href="#font-matching-examples"><span class=secno>5.6 </span>Font
       matching examples</a>
     </ul>
    <li><a href="#font-rend-props"><span class=secno>6 </span>Font Feature
     Properties</a>
     <ul class=toc>
      <li><a href="#glyph-selection-positioning"><span class=secno>6.1
       </span>Glyph selection and positioning</a>
      <li><a href="#language-specific-support"><span class=secno>6.2
       </span>Language-specific display</a>
      <li><a href="#font-kerning-prop"><span class=secno>6.3 </span>Kerning:
       the font-kerning property</a>
      <li><a href="#font-variant-ligatures-prop"><span class=secno>6.4
       </span>Ligatures: the font-variant-ligatures property</a>
      <li><a href="#font-variant-position-prop"><span class=secno>6.5
       </span>Subscript and superscript forms: the font-variant-position
       property</a>
      <li><a href="#font-variant-caps-prop"><span class=secno>6.6
       </span>Capitalization: the font-variant-caps property</a>
      <li><a href="#font-variant-numeric-prop"><span class=secno>6.7
       </span>Numerical formatting: the font-variant-numeric property</a>
      <li><a href="#font-variant-alternates-prop"><span class=secno>6.8
       </span>Alternates and swashes: the font-variant-alternates property</a>
      <li><a href="#font-feature-values"><span class=secno>6.9 </span>Defining
       font specific alternates: the <code>@font-feature-values</code>
       rule</a>
       <ul class=toc>
        <li><a href="#basic-syntax"><span class=secno>6.9.1 </span>Basic
         syntax</a>
        <li><a href="#multi-valued-feature-value-definitions"><span
         class=secno>6.9.2 </span>Multi-valued feature value definitions</a>
       </ul>
      <li><a href="#font-variant-east-asian-prop"><span class=secno>6.10
       </span>East Asian text rendering: the font-variant-east-asian
       property</a>
      <li><a href="#font-variant-prop"><span class=secno>6.11 </span>Overall
       shorthand for font rendering: the font-variant property</a>
      <li><a href="#font-feature-settings-prop"><span class=secno>6.12
       </span>Low-level font feature settings control: the
       font-feature-settings property</a>
      <li><a href="#font-language-override-prop"><span class=secno>6.13
       </span>Font language override: the font-language-override property</a>
     </ul>
    <li><a href="#font-feature-resolution"><span class=secno>7 </span>Font
     Feature Resolution </a>
     <ul class=toc>
      <li><a href="#default-features"><span class=secno>7.1 </span>Default
       features</a>
      <li><a href="#feature-precedence"><span class=secno>7.2 </span>Feature
       precedence</a>
      <li><a href="#feature-precedence-examples"><span class=secno>7.3
       </span>Feature precedence examples</a>
     </ul>
    <li><a href="#object-model"><span class=secno>8 </span>Object Model</a>
     <ul class=toc>
      <li><a href="#om-fontface"><span class=secno>8.1 </span>The
       <code>CSSFontFaceRule</code> interface</a>
      <li><a href="#om-fontfeaturevalues"><span class=secno>8.2 </span>The
       <code>CSSFontFeatureValuesRule</code> interface</a>
     </ul>
    <li class=no-num><a href="#platform-props-to-css">Appendix A: Mapping
     platform font properties to CSS properties</a>
    <li class=no-num><a href="#ch-ch-ch-changes">Changes</a>
     <ul class=toc>
      <li class=no-num><a href="#recent-changes"> Changes from the July 2013
       CSS3 Fonts Last Call Working Draft</a>
     </ul>
    <li class=no-num><a href="#acknowledgments">Acknowledgments</a>
    <li class=no-num><a href="#conformance"> Conformance</a>
     <ul class=toc>
      <li class=no-num><a href="#conventions"> Document Conventions</a>
      <li class=no-num><a href="#conformance-classes"> Conformance Classes</a>
      <li class=no-num><a href="#partial"> Partial Implementations</a>
      <li class=no-num><a href="#experimental"> Experimental
       Implementations</a>
      <li class=no-num><a href="#testing"> Non-Experimental
       Implementations</a>
     </ul>
    <li class=no-num><a href="#references">References</a>
     <ul class=toc>
      <li class=no-num><a href="#normative-references">Normative
       References</a>
      <li class=no-num><a href="#other-references">Other References</a>
     </ul>
    <li class=no-num><a href="#index">Index</a>
    <li class=no-num><a href="#property-index">Property index</a>
   </ul>
   <!--end-toc-->
   <h2 id=introduction><span class=secno>1 </span>Introduction</h2>
   <p>A font provides a resource containing the visual representation of
    characters. At the simplest level it contains information that maps
    character codes to shapes (called glyphs) that represent these characters.
    Fonts sharing a common design style are commonly grouped into font
    families classified by a set of standard font properties. Within a family,
    the shape displayed for a given character can vary by stroke weight, slant
    or relative width, among others. An individual font face is described by a
    unique combination of these properties. For a given range of text, CSS
    font properties are used to select a font family and a specific font face
    within that family to be used when rendering that text. As a simple
    example, to use the bold form of Helvetica one could use:
   <pre>body {
     font-family: Helvetica;
     font-weight: bold;
 }</pre>
   <p>Font resources may be installed locally on the system on which a user
    agent is running or downloadable. For local font resources descriptive
    information can be obtained directly from the font resource. For
    downloadable font resources (sometimes referred to as web fonts), the
    descriptive information is included with the reference to the font
    resource.
   <p>Families of fonts typically don't contain a single face for each
    possible variation of font properties. The CSS font selection mechanism
    describes how to match a given set of CSS font properties to a single font
    face.
   <h2 id=typography-background><span class=secno>2 </span>Typography
    Background</h2>
   <p><em>This section is non-normative.</em>
   <p> Typographic traditions vary across the globe, so there is no unique way
    to classify all fonts across languages and cultures. For even common Latin
    letters, wide variations are possible:
   <div class=figure><img alt="variations in glyphs for a single character"
    src=aaaaaa.png>
    <p class=caption>One character, many glyph variations
   </div>
   <p>Differences in the anatomy of letterforms is one way to distinguish
    fonts. For Latin fonts, flourishes at the ends of a character's main
    strokes, or serifs, can distinguish a font from those without. Similar
    comparisons exist in non-Latin fonts between fonts with tapered strokes
    and those using primarily uniform strokes:
   <div class=figure><img alt="serif vs. non-serifs" src=serifvssansserif.png>
    <p class=caption>Letterforms with and without serifs
   </div>
   <div class=figure><img alt="serif vs. non-serifs for japanese"
    src=minchovsgothic.png>
    <p class=caption>Similar groupings for Japanese typefaces
   </div>
   <p>Fonts contain letterforms and the data needed to map characters to these
    letterforms. Often this may be a simple one-to-one mapping, but more
    complex mappings are also possible. The use of combining diacritic marks
    creates many variations for an underlying letterform:
   <div class=figure><img alt="diacritic marks" src=aaaaaa-diacritics.png>
    <p class=caption>Variations with diacritic marks
   </div>
   <p>A sequence of characters can be represented by a single glyph known as a
    ligature:
   <div class=figure><img alt="example of a fi ligature"
    src=final-ligature.png>
    <p class=caption>Ligature example
   </div>
   <p>Visual transformations based on textual context are often stylistic
    option in European languages. They are required to correctly render
    languages like Arabic, the lam and alef characters below <em>must</em> be
    combined when they exist in sequence:
   <div class=figure><img alt="lam alef ligature" src=lamaleflig.png>
    <p class=caption>Required Arabic ligature
   </div>
   <p>The relative complexity of these shaping transformations requires
    additional data within the font.
   <p>Sets of font faces with various stylistic variations are often grouped
    together into font families. In the simplest case a regular face is
    supplemented with bold and italic faces, but much more extensive groupings
    are possible. Variations in the thickness of letterform strokes, the <dfn
    id=weight>weight</dfn>, and the overall proportions of the letterform, the
    <dfn id=width>width</dfn>, are most common. In the example below, each
    letter uses a different font face within the Univers font family. The
    width used increases from top to bottom and the weight increases from left
    to right:
   <div class=figure><img alt="various width and weight variations within a
    single family" src=weightwidthvariations.png>
    <p class=caption>Weight and width variations within a single font family
   </div>
   <p>Creating fonts that support multiple scripts is a difficult task;
    designers need to understand the cultural traditions surrounding the use
    of type in different scripts and come up with letterforms that somehow
    share a common theme. Many languages often share a common script and each
    of these languages may have noticeable stylistic differences. For example,
    the Arabic script is shared by Persian and Urdu and Cyrillic is used with
    many languages, not just Russian.
   <p>The <a href="#character-map"><em>character map</em></a> of a font
    defines the mapping of characters to glyphs for that font. If a document
    contains characters not supported by the <a href="#character-map"><em
    title="character map">character maps</em></a> of the fonts contained in a
    font family list, a user agent may use a <a
    href="#system-font-fallback"><em>system font fallback</em></a> procedure
    to locate an appropriate font that does. If no appropriate font can be
    found, some form of "missing glyph" character will be rendered by the user
    agent. System fallback can occur when the specified list of font families
    does not include a font that supports a given character.
   <p>Although the <a href="#character-map"><em>character map</em></a> of a
    font maps a given character to a glyph for that character, modern font
    technologies such as OpenType and AAT (Apple Advanced Typography) provide
    ways of mapping a character to different glyphs based upon feature
    settings. Fonts in these formats allow these features to be embedded in
    the font itself and controlled by applications. Common typographic
    features which can be specified this way include ligatures, swashes,
    contextual alternates, proportional and tabular figures, and automatic
    fractions, to list just a few. For a visual overview of OpenType features,
    see the <a href="#OPENTYPE-FONT-GUIDE"
    rel=biblioentry>[OPENTYPE-FONT-GUIDE]<!--{{OPENTYPE-FONT-GUIDE}}--></a>.
   <h2 id=basic-font-props><span class=secno>3 </span>Basic Font Properties</h2>
   <p>The particular font face used to render a character is determined by the
    font family and other font properties that apply to a given element. This
    structure allows settings to be varied independent of each other.</p>
   <!-- prop: font-family -->
   <h3 id=font-family-prop><span class=secno>3.1 </span>Font family: the <a
    href="#propdef-font-family">font-family</a> property</h3>
   <table class=propdef id=namefont-familyvalue-ltfamily-namegt-ltg>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-family
       title="font-family!!property">font-family</dfn>
     <tr>
      <td>Value:
      <td>[ <a href="#family-name-value"><var>&lt;family-name&gt;</var></a> |
       <a href="#generic-family-value"><var>&lt;generic-family&gt;</var></a> ]
       #
     <tr>
      <td>Initial:
      <td>depends on user agent
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>This property specifies a prioritized list of font family names or
    generic family names. A font family defines a set of faces that vary in
    weight, width or slope. CSS uses the combination of a family name with
    other style attributes to select an individual face. Using this selection
    mechanism, rather than selecting a face via the style name as is often
    done in design applications, allows some degree of regularity in textual
    display when fallback occurs.
   <p class=note>Designers should note that the CSS definition of font
    attributes used for selection are explicitly not intended to define a font
    taxonomy. A type designer's idea of a family may often extend to a set of
    faces that vary along axes other than just the standard axes of weight,
    width and slope. A family may extend to include both a set of serif faces
    and a set of sans-serif faces or vary along axes that are unique to that
    family. The CSS font selection mechanism merely provides a way to
    determine the “closest” substitute when substitution is necessary.
   <p>Unlike other CSS properties, component values are a comma-separated list
    indicating alternatives. A user agent iterates through the list of family
    names until it matches an available font that contains a glyph for the
    character to be rendered. This allows for differences in available fonts
    across platforms and for differences in the range of characters supported
    by individual fonts.
   <p>A font family name only specifies a name given to a set of font faces,
    it does not specify an individual face. For example, given the
    availability of the fonts below, Futura would match but Futura Medium
    would not:
   <div class=figure><img alt="family and face names"
    src=familyvsfacename.png>
    <p class=caption>Family and individual face names
   </div>
   <p>Consider the example below:
   <div class=example>
    <pre>body {
     font-family: Helvetica, Verdana, sans-serif;
 }</pre>
    <p>If Helvetica is available it will be used when rendering. If neither
     Helvetica nor Verdana is present, then the user-agent-defined sans serif
     font will be used.</p>
   </div>
   <p>There are two types of font family names:
   <dl>
    <dt><dfn id=family-name-value><var>&lt;family-name&gt;</var></dfn>
    <dd>The name of a font family of choice such as Helvetica or Verdana in
     the previous example.
    <dt><dfn id=generic-family-value><var>&lt;generic-family&gt;</var></dfn>
    <dd> The following generic family keywords are defined: ‘<a
     href="#serif"><code class=property>serif</code></a>’, ‘<a
     href="#sans-serif"><code class=property>sans-serif</code></a>’, ‘<a
     href="#cursive"><code class=property>cursive</code></a>’, ‘<a
     href="#fantasy"><code class=property>fantasy</code></a>’, and ‘<a
     href="#monospace"><code class=property>monospace</code></a>’. These
     keywords can be used as a general fallback mechanism when an author's
     desired font choices are not available. As keywords, they must not be
     quoted. Authors are encouraged to append a generic font family as a last
     alternative for improved robustness.
   </dl>
   <p>Font family names other than generic families must either be given
    quoted as <a
    href="http://www.w3.org/TR/CSS21/syndata.html#strings">strings,</a> or
    unquoted as a sequence of one or more <a
    href="http://www.w3.org/TR/CSS21/syndata.html#value-def-identifier">identifiers.</a>
    This means most punctuation characters and digits at the start of each
    token must be escaped in unquoted font family names.
   <p>To illustrate this, the following declarations are invalid:
   <pre>
 font-family: Red/Black, sans-serif;
 font-family: "Lucida" Grande, sans-serif;
 font-family: Ahem!, sans-serif;
 font-family: test@foo, sans-serif;
 font-family: #POUND, sans-serif;
 font-family: Hawaii 5-0, sans-serif;
 </pre>
   <p>If a sequence of identifiers is given as a font family name, the
    computed value is the name converted to a string by joining all the
    identifiers in the sequence by single spaces.
   <p>To avoid mistakes in escaping, it is recommended to quote font family
    names that contain white space, digits, or punctuation characters other
    than hyphens:
   <pre>
 body { font-family: "New Century Schoolbook", serif }
 &lt;BODY STYLE="font-family: '21st Century', fantasy">
 </pre>
   <p>Font family <em>names</em> that happen to be the same as a keyword value
    (‘<code class=property>inherit</code>’, ‘<a href="#serif"><code
    class=property>serif</code></a>’, ‘<a href="#sans-serif"><code
    class=property>sans-serif</code></a>’, ‘<a href="#monospace"><code
    class=property>monospace</code></a>’, ‘<a href="#fantasy"><code
    class=property>fantasy</code></a>’, and ‘<a href="#cursive"><code
    class=property>cursive</code></a>’) must be quoted to prevent confusion
    with the keywords with the same names. The keywords ‘<code
    class=property>initial</code>’ and ‘<code
    class=property>default</code>’ are reserved for future use and must also
    be quoted when used as font names. UAs must not consider these keywords as
    matching the <a
    href="#family-name-value"><var>&lt;family-name&gt;</var></a> type.
   <p>The precise way a set of fonts are grouped into font families varies
    depending upon the platform font management API's. The Windows GDI API
    only allows four faces to be grouped into a family while the DirectWrite
    API and API's on OSX and other platforms support font families with a
    variety of weights, widths and slopes (see <a
    href="#platform-props-to-css">Appendix A</a> for more details).
   <p>Some font formats allow fonts to carry multiple localizations of the
    family name. User agents must recognize and correctly match all of these
    names independent of the underlying platform localization, system API used
    or document encoding:
   <div class=figure><img alt="examples of localized family names"
    src=localizedfamilynames.png>
    <p class=caption>Localized family names
   </div>
   <h4 id=generic-font-families><span class=secno>3.1.1 </span>Generic font
    families</h4>
   <p>All five generic font families are defined to exist in all CSS
    implementations (they need not necessarily map to five distinct actual
    fonts). User agents should provide reasonable default choices for the
    generic font families, which express the characteristics of each family as
    well as possible within the limits allowed by the underlying technology.
    User agents are encouraged to allow users to select alternative choices
    for the generic fonts.
   <h5 class="no-num no-toc"> <span class=index-def id=serif0 title="serif,
    definition of"><a name=serif-def><dfn id=serif>serif</dfn></a></span></h5>
   <p>Serif fonts represent the formal text style for a script. This often
    means but is not limited to glyphs that have finishing strokes, flared or
    tapering ends, or have actual serifed endings (including slab serifs).
    Serif fonts are typically proportionately-spaced. They often display a
    greater variation between thick and thin strokes than fonts from the ‘<a
    href="#sans-serif"><code class=property>sans-serif</code></a>’ generic
    font family. CSS uses the term ‘<a href="#serif"><code
    class=property>serif</code></a>’ to apply to a font for any script,
    although other names may be more familiar for particular scripts, such as
    Mincho (Japanese), Sung, Song or Kai (Chinese), Batang (Korean). For
    Arabic, the Naskh style would correspond to ‘<a href="#serif"><code
    class=property>serif</code></a>’ more due to its typographic role rather
    than its actual design style. Any font that is so described may be used to
    represent the generic ‘<a href="#serif"><code
    class=property>serif</code></a>’ family.
   <div class=figure><img alt="sample serif fonts" src=serifexamples.png>
    <p class=caption>Sample serif fonts
   </div>
   <h5 class="no-num no-toc"> <span class=index-def id=sans-serif0
    title="sans-serif, definition of"> <a name=sans-serif-def><dfn
    id=sans-serif>sans-serif</dfn></a></span></h5>
   <p>Glyphs in sans-serif fonts, as the term is used in CSS, are generally
    low contrast (vertical and horizontal stems have the close to the same
    thickness) and have stroke endings that are plain -- without any flaring,
    cross stroke, or other ornamentation. Sans-serif fonts are typically
    proportionately-spaced. They often have little variation between thick and
    thin strokes, compared to fonts from the ‘<a href="#serif"><code
    class=property>serif</code></a>’ family. CSS uses the term ‘<a
    href="#sans-serif"><code class=property>sans-serif</code></a>’ to apply
    to a font for any script, although other names may be more familiar for
    particular scripts, such as Gothic (Japanese), Hei (Chinese), or Gulim
    (Korean). Any font that is so described may be used to represent the
    generic ‘<a href="#sans-serif"><code
    class=property>sans-serif</code></a>’ family.
   <div class=figure><img alt="sample sans-serif fonts"
    src=sansserifexamples.png>
    <p class=caption>Sample sans-serif fonts
   </div>
   <h5 class="no-num no-toc"> <span class=index-def id=cursive0
    title="cursive, definition of"> <a name=cursive-def><dfn
    id=cursive>cursive</dfn></a></span></h5>
   <p>Glyphs in cursive fonts generally use a more informal script style, and
    the result looks more like handwritten pen or brush writing than printed
    letterwork. CSS uses the term ‘<a href="#cursive"><code
    class=property>cursive</code></a>’ to apply to a font for any script,
    although other names such as Chancery, Brush, Swing and Script are also
    used in font names.
   <div class=figure><img alt="sample cursive fonts" src=cursiveexamples.png>
    <p class=caption>Sample cursive fonts
   </div>
   <h5 class="no-num no-toc"> <span class=index-def id=fantasy0
    title="fantasy, definition of"> <a name=fantasy-def><dfn
    id=fantasy>fantasy</dfn></a></span></h5>
   <p>Fantasy fonts are primarily decorative or expressive fonts that contain
    playful representations of characters. These do not include Pi or Picture
    fonts which do not represent actual characters.
   <div class=figure><img alt="sample fantasy fonts" src=fantasyexamples.png>
    <p class=caption>Sample fantasy fonts
   </div>
   <h5 class="no-num no-toc"> <span class=index-def id=monospace0
    title="monospace, definition of"> <a name=monospace-def><dfn
    id=monospace>monospace</dfn></a></span></h5>
   <p>The sole criterion of a monospace font is that all glyphs have the same
    fixed width. This is often used to render samples of computer code.
   <div class=figure><img alt="sample monospace fonts"
    src=monospaceexamples.png>
    <p class=caption>Sample monospace fonts
   </div>
   <!-- prop: font-weight -->
   <h3 id=font-weight-prop><span class=secno>3.2 </span>Font weight: the <a
    href="#propdef-font-weight">font-weight</a> property</h3>
   <table class=propdef id=namefont-weightvaluenormal-bold-bolder-l>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-weight
       title="font-weight!!property">font-weight</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-weight-normal-value"
       title="normal!!font-weight">normal</a> | <a href="#bold">bold</a> | <a
       href="#bolder">bolder</a> | <a href="#lighter">lighter</a> | <a
       href="#font-weight-numeric-values" title="100...900 weight
       values">100</a> | <a href="#font-weight-numeric-values"
       title="100...900 weight values">200</a> | <a
       href="#font-weight-numeric-values" title="100...900 weight
       values">300</a> | <a href="#font-weight-numeric-values"
       title="100...900 weight values">400</a> | <a
       href="#font-weight-numeric-values" title="100...900 weight
       values">500</a> | <a href="#font-weight-numeric-values"
       title="100...900 weight values">600</a> | <a
       href="#font-weight-numeric-values" title="100...900 weight
       values">700</a> | <a href="#font-weight-numeric-values"
       title="100...900 weight values">800</a> | <a
       href="#font-weight-numeric-values" title="100...900 weight
       values">900</a>
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>numeric weight value (see description)
     <tr>
      <td>Animatable:
      <td>as <a
       href="http://dev.w3.org/csswg/css3-transitions/#animtype-font-weight">font
       weight</a>
   </table>
   <p>The <a href="#propdef-font-weight"
    title="font-weight!!property">‘<code
    class=property>font-weight</code>’</a> property specifies the weight of
    glyphs in the font, their degree of blackness or stroke thickness.
   <p>Values have the following meanings:
   <dl>
    <dt><dfn id=font-weight-numeric-values title="100...900 weight values">100
     to 900</dfn>
    <dd>These values form an ordered sequence, where each number indicates a
     weight that is at least as dark as its predecessor. These roughly
     correspond to the commonly used weight names below:
   </dl>
   <ul>
    <li>100 - Thin
    <li>200 - Extra Light (Ultra Light)
    <li>300 - Light
    <li>400 - Normal
    <li>500 - Medium
    <li>600 - Semi Bold (Demi Bold)
    <li>700 - Bold
    <li>800 - Extra Bold (Ultra Bold)
    <li>900 - Black (Heavy)
   </ul>
   <dl>
    <dt><dfn id=font-weight-normal-value
     title="normal!!font-weight">normal</dfn>
    <dd>Same as ‘<code class=css>400</code>’.
    <dt><dfn id=bold>bold</dfn>
    <dd>Same as ‘<code class=css>700</code>’.
    <dt><dfn id=bolder>bolder</dfn>
    <dd>Specifies a bolder weight than the inherited value.
    <dt><dfn id=lighter>lighter</dfn>
    <dd>Specifies a lighter weight than the inherited value.
   </dl>
   <p>Font formats that use a scale other than a nine-step scale should map
    their scale onto the CSS scale so that 400 roughly corresponds with a face
    that would be labeled as Regular, Book, Roman and 700 roughly matches a
    face that would be labeled as Bold. Or weights may be inferred from the
    style names, ones that correspond roughly with the scale above. The scale
    is relative, so a face with a larger weight value must never appear
    lighter. If style names are used to infer weights, care should be taken to
    handle variations in style names across locales.
   <p>Quite often there are only a few weights available for a particular font
    family. When a weight is specified for which no face exists, a face with a
    nearby weight is used. In general, bold weights map to faces with heavier
    weights and light weights map to faces with lighter weights (see the <a
    href="#font-matching-algorithm">font matching section below</a> for a
    precise definition). The examples here illustrate which face is used for
    different weights, grey indicates a face for that weight does not exist so
    a face with a nearby weight is used:
   <div class=figure><img alt="weight mappings for a family with 400, 700 and
 weights" src=optimaweights.png>
    <p class=caption>Weight mappings for a font family with 400, 700 and 900
     weight faces
   </div>
   <div class=figure><img alt="weight mappings for a family with 300, 600
    weights" src=hiraginoweights.png>
    <p class=caption>Weight mappings for a font family with 300 and 600 weight
     faces
   </div>
   <p>Although the practice is not well-loved by typographers, bold faces are
    often synthesized by user agents for faces that lack actual bold faces.
    For the purposes of style matching, these faces must be treated as if they
    exist within the family. Authors can explicitly avoid this behavior by
    using the ‘<a href="#propdef-font-synthesis"><code
    class=property>font-synthesis</code></a>’ property.
   <p>Specified values of ‘<a href="#bolder"><code
    class=property>bolder</code></a>’ and ‘<a href="#lighter"><code
    class=property>lighter</code></a>’ indicate weights relative to the
    weight of the parent element. The computed weight is calculated based on
    the inherited <a href="#propdef-font-weight"
    title="font-weight!!property">‘<code
    class=property>font-weight</code>’</a> value using the chart below.
   <table class=data id=bolderlighter summary="Bolder/lighter mappings">
    <thead>
     <tr>
      <th>Inherited value
      <th>bolder
      <th>lighter
    <tbody>
     <tr>
      <th>100
      <td>400
      <td>100
     <tr>
      <th>200
      <td>400
      <td>100
     <tr>
      <th>300
      <td>400
      <td>100
     <tr>
      <th>400
      <td>700
      <td>100
     <tr>
      <th>500
      <td>700
      <td>100
     <tr>
      <th>600
      <td>900
      <td>400
     <tr>
      <th>700
      <td>900
      <td>400
     <tr>
      <th>800
      <td>900
      <td>700
     <tr>
      <th>900
      <td>900
      <td>700
   </table>
   <p>The table above is equivalent to selecting the next relative bolder or
    lighter face, given a font family containing normal and bold faces along
    with a thin and a heavy face. Authors who desire finer control over the
    exact weight values used for a given element may use numerical values
    instead of relative weights.</p>
   <!-- prop: font-stretch -->
   <h3 id=font-stretch-prop><span class=secno>3.3 </span>Font width: the <a
    href="#propdef-font-stretch">font-stretch</a> property</h3>
   <table class=propdef id=namefont-stretchvalue-normal-ultra-conde>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-stretch
       title="font-stretch!!property">font-stretch</dfn>
     <tr>
      <td>Value:
      <td> <a href="#font-stretch-normal-value"
       title="normal!!font-stretch">normal</a> | <a
       href="#ultra-condensed">ultra-condensed</a> | <a
       href="#extra-condensed">extra-condensed</a> | <a
       href="#condensed">condensed</a> | <a
       href="#semi-condensed-">semi-condensed</a> | <a
       href="#semi-expanded">semi-expanded</a> | <a
       href="#expanded">expanded</a> | <a
       href="#extra-expanded">extra-expanded</a> | <a
       href="#ultra-expanded">ultra-expanded</a>
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>as <a href="#font-stretch-animation">font stretch</a>
   </table>
   <p>The <a href="#propdef-font-stretch"
    title="font-stretch!!property">‘<code
    class=property>font-stretch</code>’</a> property selects a normal,
    condensed, or expanded face from a font family. Absolute keyword values
    have the following ordering, from narrowest to widest:
   <ul>
    <li><dfn id=ultra-condensed>ultra-condensed</dfn>
    <li><dfn id=extra-condensed>extra-condensed</dfn>
    <li><dfn id=condensed>condensed</dfn>
    <li><dfn id=semi-condensed->semi-condensed </dfn>
    <li><dfn id=font-stretch-normal-value
     title="normal!!font-stretch">normal</dfn>
    <li><dfn id=semi-expanded>semi-expanded</dfn>
    <li><dfn id=expanded>expanded</dfn>
    <li><dfn id=extra-expanded>extra-expanded</dfn>
    <li><dfn id=ultra-expanded>ultra-expanded</dfn>
   </ul>
   <p>When a face does not exist for a given width, normal or condensed values
    map to a narrower face, otherwise a wider face. Conversely, expanded
    values map to a wider face, otherwise a narrower face. The figure below
    shows how the nine font-stretch property settings affect font selection
    for font family containing a variety of widths, grey indicates a width for
    which no face exists and a different width is substituted:
   <div class=figure><img alt="width mappings for a family with condensed,
    normal and expanded faces" src=universwidths.png>
    <p class=caption>Width mappings for a font family with condensed, normal
     and expanded width faces
   </div>
   <p id=font-stretch-animation>Animation of font stretch: Font stretch is
    interpolated in discrete steps. The interpolation happens as though the
    ordered values are equally spaced real numbers. The interpolation result
    is rounded to the nearest value, with values exactly halfway between two
    values rounded towards the later value in the list above.</p>
   <!-- prop: font-style -->
   <h3 id=font-style-prop><span class=secno>3.4 </span>Font style: the <a
    href="#propdef-font-style">font-style</a> property</h3>
   <table class=propdef id=namefont-stylevaluenormal-italic-oblique>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-style
       title="font-style!!property">font-style</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-style-normal-value"
       title="normal!!font-style">normal</a> | <a href="#italic">italic</a> |
       <a href="#oblique">oblique</a>
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>The <a href="#propdef-font-style" title="font-style!!property">‘<code
    class=property>font-style</code>’</a> property allows italic or oblique
    faces to be selected. Italic forms are generally cursive in nature while
    oblique faces are typically sloped versions of the regular face. Oblique
    faces can be simulated by artificially sloping the glyphs of the regular
    face. Compare the artificially sloped renderings of Palatino ‘<code
    class=property>a</code>’ and Baskerville ‘<code
    class=property>N</code>’ in grey with the actual italic versions:
   <div class=figure><img alt="artificial sloping vs. real italics"
    src=realvsfakeitalics.png>
    <p class=caption>Artificial sloping versus real italics
   </div>
   <p>Values have the following meanings:
   <dl>
    <dt><dfn id=font-style-normal-value
     title="normal!!font-style">normal</dfn>
    <dd>selects a face that is classified as a normal face, one that is
     neither italic or obliqued
    <dt><dfn id=italic>italic</dfn>
    <dd>selects a font that is labeled as an italic face, or an oblique face
     if one is not
    <dt><dfn id=oblique>oblique</dfn>
    <dd>selects a font that is labeled as an oblique face, or an italic face
     if one is not
   </dl>
   <p>If no italic or oblique face is available, oblique faces can be
    synthesized by rendering non-obliqued faces with an artificial obliquing
    operation. The use of these artificially obliqued faces can be disabled
    using the ‘<a href="#propdef-font-synthesis"><code
    class=property>font-synthesis</code></a>’ property. The details of the
    obliquing operation are not explicitly defined.</p>
   <!-- resolution on the "undefined" nature of synthetics: http://www.w3.org/2013/06/06-css-minutes.html#item03 -->
   <p>Many scripts lack the tradition of mixing a cursive form within text
    rendered with a normal face. Chinese, Japanese and Korean fonts almost
    always lack italic or oblique faces. Fonts that support a mixture of
    scripts will sometimes omit specific scripts such as Arabic from the set
    of glyphs supported in the italic face. User agents should be careful
    about making <a href="#character-map"><em>character map</em></a>
    assumptions across faces when implementing support for <a
    href="#system-font-fallback"><em>system font fallback</em></a>.</p>
   <!-- prop: font-size -->
   <h3 id=font-size-prop><span class=secno>3.5 </span>Font size: the <a
    href="#propdef-font-size">font-size</a> property</h3>
   <table class=propdef id=namefont-sizevalueltabsolute-sizegt-ltre>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-size>font-size</dfn>
     <tr>
      <td>Value:
      <td><a href="#absolute-size-value"><var>&lt;absolute-size&gt;</var></a>
       | <a href="#relative-size-value"><var>&lt;relative-size&gt;</var></a> |
       <a href="#length-size-value"><var>&lt;length&gt;</var></a> | <a
       href="#percentage-size-value"><var>&lt;percentage&gt;</var></a>
     <tr>
      <td>Initial:
      <td>medium
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>refer to parent element's font size
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>absolute length
     <tr>
      <td>Animatable:
      <td>as <a
       href="http://dev.w3.org/csswg/css3-transitions/#animtype-length">length</a>
   </table>
   <p>This property indicates the desired height of glyphs from the font. For
    scalable fonts, the font-size is a scale factor applied to the EM unit of
    the font. (Note that certain glyphs may bleed outside their EM box.) For
    non-scalable fonts, the font-size is converted into absolute units and
    matched against the declared font-size of the font, using the same
    absolute coordinate space for both of the matched values. Values have the
    following meanings:
   <dl>
    <dt><dfn id=absolute-size-value><var>&lt;absolute-size&gt;</var></dfn>
    <dd> An <a
     href="#absolute-size-value"><var>&lt;absolute-size&gt;</var></a> keyword
     refers to an entry in a table of font sizes computed and kept by the user
     agent. Possible values are:
     <p> [ xx-small | x-small | small | medium | large | x-large | xx-large ]</p>
    <dt><dfn id=relative-size-value><var>&lt;relative-size&gt;</var></dfn>
    <dd> A <a href="#relative-size-value"><var>&lt;relative-size&gt;</var></a>
     keyword is interpreted relative to the table of font sizes and the
     computed ‘<a href="#propdef-font-size"><code
     class=property>font-size</code></a>’ of the parent element. Possible
     values are:
     <p> [ larger | smaller ]
     <p> For example, if the parent element has a font size of ‘<code
      class=property>medium</code>’, a value of ‘<code
      class=property>larger</code>’ will make the font size of the current
      element be ‘<code class=property>large</code>’. If the parent
      element's size is not close to a table entry, the user agent is free to
      interpolate between table entries or round off to the closest one. The
      user agent may have to extrapolate table values if the numerical value
      goes beyond the keywords.
    <dt><dfn id=length-size-value><var>&lt;length&gt;</var></dfn>
    <dd>A length value specifies an absolute font size (independent of the
     user agent's font table). Negative lengths are illegal.
    <dt><dfn id=percentage-size-value><var>&lt;percentage&gt;</var></dfn>
    <dd>A percentage value specifies an absolute font size relative to the
     parent element's font size. Use of percentage values, or values in
     ‘<code class=property>em</code>’s, leads to more robust and
     cascadable style sheets.
   </dl>
   <p>The following table provides user agent guidelines for the absolute-size
    scaling factor and their mapping to HTML heading and absolute font-sizes.
    The ‘<code class=property>medium</code>’ value is used as the
    reference middle value. The user agent may fine-tune these values for
    different fonts or different types of display devices.
   <table class=data>
    <thead>
     <tr>
      <th>CSS absolute-size values
      <th>xx-small
      <th>x-small
      <th>small
      <th>medium
      <th>large
      <th>x-large
      <th>xx-large
      <th>
    <tbody>
     <tr>
      <th>scaling factor
      <td>3/5
      <td>3/4
      <td>8/9
      <td>1
      <td>6/5
      <td>3/2
      <td>2/1
      <td>3/1
     <tr>
      <th>HTML headings
      <td>h6
      <td>
      <td>h5
      <td>h4
      <td>h3
      <td>h2
      <td>h1
      <td>
     <tr>
      <th>HTML font sizes
      <td>1
      <td>
      <td>2
      <td>3
      <td>4
      <td>5
      <td>6
      <td>7
   </table>
   <p class=note><em><strong>Note 1.</strong> To preserve readability, an UA
    applying these guidelines should nevertheless avoid creating font-size
    resulting in less than 9 device pixels per EM unit on a computer
    display.</em>
   <p class=note><em><strong>Note 2.</strong> In CSS1, the suggested scaling
    factor between adjacent indexes was 1.5 which user experience proved to be
    too large. In CSS2, the suggested scaling factor for computer screen
    between adjacent indexes was 1.2 which still created issues for the small
    sizes. The new scaling factor varies between each index to provide a
    better readability.</em>
   <p>The actual value of this property may differ from the computed value due
    a numerical value on ‘<a href="#propdef-font-size-adjust"><code
    class=property>font-size-adjust</code></a>’ and the unavailability of
    certain font sizes.
   <p>Child elements inherit the computed <a class=noxref
    href="#font-size-prop"> <span class=property>‘<code
    class=property>font-size</code>’</span></a> value (otherwise, the effect
    of <a class=noxref href="#font-size-adjust-prop"><span
    class=property>‘<code
    class=property>font-size-adjust</code>’</span></a> would compound).
   <div class=example>
    <p style="display:none">Example(s):</p>
    <pre>p { font-size: 12pt; }
 blockquote { font-size: larger }
 em { font-size: 150% }
 em { font-size: 1.5em }
 </pre>
   </div>
   <!-- prop: font-size-adjust -->
   <h3 id=font-size-adjust-prop><span class=secno>3.6 </span>Relative sizing:
    the <a href="#propdef-font-size-adjust">font-size-adjust</a> property</h3>
   <table class=propdef id=namefont-size-adjustvaluenone-auto-ltnum>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-size-adjust>font-size-adjust</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-size-adjust-none-value"
       title="none!!font-size-adjust">none</a> | <a
       href="#font-size-adjust-auto-value"
       title="auto!!font-size-adjust">auto</a> | <a
       href="#aspect-ratio-value"><var>&lt;number&gt;</var></a>
     <tr>
      <td>Initial:
      <td>none
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>as <a
       href="http://dev.w3.org/csswg/css3-transitions/#animtype-number">number</a>
   </table>
   <p>For any given font size, the apparent size and legibility of text varies
    across fonts. For scripts such as Latin or Cyrillic that distinguish
    between upper and lowercase letters, the relative height of lowercase
    letters compared to their uppercase counterparts is a determining factor
    of legibility. This is commonly referred to as the <a class=index-def
    href="#aspect-value" id=aspect-value0 title="aspect value"><dfn
    id=aspect-value>aspect value</dfn></a>. Precisely defined, it is equal to
    the x-height of a font divided by the font size.
   <p>In situations where font fallback occurs, fallback fonts may not share
    the same aspect ratio as the desired font family and will thus appear less
    readable. The font-size-adjust property is a way to preserve the
    readability of text when font fallback occurs. It does this by adjusting
    the font-size so that the x-height is the same regardless of the font
    used.
   <div class=example>
    <p>The style defined below defines Verdana as the desired font family, but
     if Verdana is not available Futura or Times will be used.</p>
    <pre>p {
     font-family: Verdana, Futura, Times;
 }
 &lt;p>Lorem ipsum dolor sit amet, ...&lt;/p>
 </pre>
    <p>Verdana has a relatively high aspect ratio, lowercase letters are
     relatively tall compared to uppercase letters, so at small sizes text
     appears legible. Times has a lower aspect ratio and so if fallback
     occurs, the text will be less legible at small sizes than Verdana.</p>
   </div>
   <p>How text rendered in each of these fonts compares is shown below, the
    columns show text rendered in Verdana, Futura and Times. The same
    font-size value is used across cells within each row and red lines are
    included to show the differences in x-height. In the upper half each row
    is rendered in the same font-size value. The same is true for the lower
    half but in this half the font-size-adjust property is also set so that
    the actual font size is adjusted to preserve the x-height across each row.
    Note how small text remains relatively legible across each row in the
    lower half.
   <div class=figure><img alt="text with and without font-size-adjust"
    src=fontsizeadjust.png>
    <p class=caption>Text with and without the use of font-size-adjust
   </div>
   <p>This property allows authors to specify an <a
    href="#aspect-value"><i>aspect value</i></a> for an element that will
    effectively preserve the x-height of the first choice font, whether it is
    substituted or not. Values have the following meanings:
   <dl>
    <dt><dfn id=font-size-adjust-none-value
     title="none!!font-size-adjust">none</dfn>
    <dd>Do not preserve the font's x-height.
    <dt><dfn id=font-size-adjust-auto-value
     title="auto!!font-size-adjust">auto</dfn>
    <dd>Behaves just like &lt;number>, except the number used is the <a
     href="#aspect-value"><i>aspect value</i></a> calculated by user agents
     for the first font in the list of fonts defined for the initial value of
     the <a href="#propdef-font-family" title="font-family!!property">‘<code
     class=property>font-family</code>’</a> property. Effectively this is
     the default font used for basic Latin text when <a
     href="#propdef-font-family" title="font-family!!property">‘<code
     class=property>font-family</code>’</a> is not otherwise specified. It
     does not vary based on document content and it is not calculated based on
     the computed value of <a href="#propdef-font-family"
     title="font-family!!property">‘<code
     class=property>font-family</code>’</a> for a given element.
     <p class=note>Authors can use this value to specify that font size should
      be normalized across fonts based on the x-height without the need to
      specify the aspect value explicitly.</p>
    <dt><dfn id=aspect-ratio-value><var>&lt;number&gt;</var></dfn>
    <dd>Specifies the <a href="#aspect-value"><i>aspect value</i></a> used in
     the calculation below to calculate the adjusted font size:
     <pre>c  =  ( a / a' ) s
 </pre>
     <p>where:</p>
     <pre>s  =  font-size value
 a  =  <a href="#aspect-value"><i>aspect value</i></a> as specified by the font-size-adjust property
 a' =  <a href="#aspect-value"><i>aspect value</i></a> of actual font
 c  =  adjusted font-size to use
 </pre>
     <p>This value applies to any font that is selected but in typical usage
      it should be based on the <a href="#aspect-value"><i>aspect
      value</i></a> of the first font in the font-family list. If this is
      specified accurately, the <tt>(a/a')</tt> term in the formula above is
      effectively 1 for the first font and no adjustment occurs. If the value
      is specified inaccurately, text rendered using the first font in the
      family list will display differently in older user agents that don't
      support font-size-adjust.</p>
   </dl>
   <p>The value of ‘<a href="#propdef-font-size-adjust"><code
    class=property>font-size-adjust</code></a>’ affects the size of relative
    units that are based on font metrics of the <a
    href="#first-available-font"><i>first available font</i></a> such as
    <code>ex</code> and <code>ch</code> but does not affect the size of
    <code>em</code> units.
   <p>Authors can calculate the <a href="#aspect-value"><i>aspect
    value</i></a> for a given font by comparing spans with the same content
    but different font-size-adjust properties. If the same font-size is used,
    the spans will match when the font-size-adjust value is accurate for the
    given font.
   <div class=example>
    <p>Two spans with borders are used to determine the <a
     href="#aspect-value"><i>aspect value</i></a> of a font. The font-size is
     the same for both spans but the font-size-adjust property is specified
     only for the right span. Starting with a value of 0.5, the aspect value
     can be adjusted until the borders around the two letters line up.</p>
    <pre>p {
     font-family: Futura;
     font-size: 500px;
 }
 span {
     border: solid 1px red;
 }
 .adjust {
     font-size-adjust: 0.5;
 }
 &lt;p>&lt;span>b&lt;/span>&lt;span class="adjust">b&lt;/span>&lt;/p>
 </pre>
    <div class=figure><img alt="Futura with an <i>aspect value</i> of 0.5"
     src=beforefontsizeadjust.png>
     <p class=caption>Futura with an <a href="#aspect-value"><i>aspect
      value</i></a> of 0.5
    </div>
    <p>The box on the right is a bit bigger than the one on the left, so the
     <a href="#aspect-value"><i>aspect value</i></a> of this font is something
     less than 0.5. Adjust the value until the boxes align.</p>
   </div>
   <!-- prop: font -->
   <h3 id=font-prop><span class=secno>3.7 </span>Shorthand font property: the
    <a href="#propdef-font">font</a> property</h3>
   <table class=propdef id=namefontvalue-ltlsquofont-stylersquogt-l>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font>font</dfn>
     <tr>
      <td>Value:
      <td>[ [ <var>&lt;<a href="#propdef-font-style"
       title="font-style!!property">‘<code
       class=property>font-style</code>’</a>&gt;</var> || <a
       href="#font-variant-css21-values"><var>&lt;font-variant-css21&gt;</var></a>
       || <var>&lt;<a href="#propdef-font-weight"
       title="font-weight!!property">‘<code
       class=property>font-weight</code>’</a>&gt;</var> || <var>&lt;<a
       href="#propdef-font-stretch" title="font-stretch!!property">‘<code
       class=property>font-stretch</code>’</a></var> ]? <var>&lt;‘<a
       href="#propdef-font-size"><code
       class=property>font-size</code></a>’&gt;</var> [ / <var>&lt;‘<code
       class=property>line-height</code>’&gt;</var> ]? <var>&lt;<a
       href="#propdef-font-family" title="font-family!!property">‘<code
       class=property>font-family</code>’</a>&gt;</var> ] | caption | icon |
       menu | message-box | small-caption | status-bar
     <tr>
      <td>Initial:
      <td>see individual properties
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>see individual properties
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>see individual properties
     <tr>
      <td>Animatable:
      <td>see individual properties
   </table>
   <p>The <span class=property>‘<a href="#propdef-font"><code
    class=property>font</code></a>’</span> property is, except as described
    below, a shorthand property for setting <a href="#propdef-font-style"
    title="font-style!!property">‘<code
    class=property>font-style</code>’</a>, <a href="#propdef-font-variant"
    title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a>, <a href="#propdef-font-weight"
    title="font-weight!!property">‘<code
    class=property>font-weight</code>’</a>, <a href="#propdef-font-stretch"
    title="font-stretch!!property">‘<code
    class=property>font-stretch</code>’</a>, <span class=property>‘<a
    href="#propdef-font-size"><code
    class=property>font-size</code></a>’</span>, <a class=property
    href="http://www.w3.org/TR/CSS2/visudet.html#propdef-line-height">‘<code
    class=property>line-height</code>’</a>, <a href="#propdef-font-family"
    title="font-family!!property">‘<code
    class=property>font-family</code>’</a> at the same place in the
    stylesheet. Values for the <a href="#propdef-font-variant"
    title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> property may also be included
    but only those supported in CSS 2.1, none of the <a
    href="#propdef-font-variant" title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> values added in this
    specification can be used in the <span class=property>‘<a
    href="#propdef-font"><code class=property>font</code></a>’</span>
    shorthand:
   <pre
    class=prod><dfn id=font-variant-css21-values><var>&lt;font-variant-css21&gt;</var></dfn> = [normal | small-caps]</pre>
   <p>The syntax of this property is based on a traditional typographical
    shorthand notation to set multiple properties related to fonts.
   <p>All subproperties of the ‘<a href="#propdef-font"><code
    class=property>font</code></a>’ property are first reset to their
    initial values, including those listed above plus <span
    class=property>‘<a href="#propdef-font-size-adjust"><code
    class=property>font-size-adjust</code></a>’</span>, <span
    class=property>‘<a href="#propdef-font-kerning"><code
    class=property>font-kerning</code></a>’</span>, subproperties of <a
    href="#propdef-font-variant" title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> and and <span>‘<a
    href="#propdef-font-language-override"><code
    class=property>font-language-override</code></a>’</span>. Then, those
    properties that are given explicit values in the <span
    class=property>‘<a href="#propdef-font"><code
    class=property>font</code></a>’</span> shorthand are set to those
    values. For a definition of allowed and initial values, see the previously
    defined properties. For reasons of backwards compatibility, it is not
    possible to set <span class=property>‘<a
    href="#propdef-font-size-adjust"><code
    class=property>font-size-adjust</code></a>’</span> to anything other
    than its initial value using the <span class=property>‘<a
    href="#propdef-font"><code class=property>font</code></a>’</span>
    shorthand property; instead, use the individual property.
   <div class=example>
    <p style="display:none">Example(s):</p>
    <pre>p { font: 12pt/14pt sans-serif }
 p { font: 80% sans-serif }
 p { font: x-large/110% &quot;new century schoolbook&quot;, serif }
 p { font: bold italic large Palatino, serif }
 p { font: normal small-caps 120%/120% fantasy }
 p { font: condensed oblique 12pt &quot;Helvetica Neue&quot;, serif; }
 </pre>
    <p> In the second rule, the font size percentage value (‘<code
     class=css>80%</code>’) refers to the computed ‘<a
     href="#propdef-font-size"><code class=property>font-size</code></a>’ of
     the parent element. In the third rule, the line height percentage
     (‘<code class=css>110%</code>’) refers to the font size of the
     element itself.
    <p>The first three rules do not specify the <a
     href="#propdef-font-variant" title="font-variant!!property">‘<code
     class=property>font-variant</code>’</a> and <a
     href="#propdef-font-weight" title="font-weight!!property">‘<code
     class=property>font-weight</code>’</a> explicitly, so these properties
     receive their initial values (<span title="normal value">‘<code
     class=property>normal</code>’</span>). Notice that the font family name
     "new century schoolbook", which contains spaces, is enclosed in quotes.
     The fourth rule sets the <a href="#propdef-font-weight"
     title="font-weight!!property">‘<code
     class=property>font-weight</code>’</a> to ‘<a href="#bold"><code
     class=property>bold</code></a>’, the <a href="#propdef-font-style"
     title="font-style!!property">‘<code
     class=property>font-style</code>’</a> to ‘<a href="#italic"><code
     class=property>italic</code></a>’, and implicitly sets <a
     href="#propdef-font-variant" title="font-variant!!property">‘<code
     class=property>font-variant</code>’</a> to <a
     href="#font-variant-normal-value" title="normal!!font-variant">‘<code
     class=property>normal</code>’</a>.
    <p> The fifth rule sets the <a href="#propdef-font-variant"
     title="font-variant!!property">‘<code
     class=property>font-variant</code>’</a> (‘<a href="#small-caps"><code
     class=property>small-caps</code></a>’), the <span class=property>‘<a
     href="#propdef-font-size"><code
     class=property>font-size</code></a>’</span> (120% of the parent's font
     size), the <a class=property
     href="http://www.w3.org/TR/CSS2/visudet.html#propdef-line-height">‘<code
     class=property>line-height</code>’</a> (120% of the font size) and the
     <a href="#propdef-font-family" title="font-family!!property">‘<code
     class=property>font-family</code>’</a> (‘<a href="#fantasy"><code
     class=property>fantasy</code></a>’). It follows that the keyword <span
     title="normal value">‘<code class=property>normal</code>’</span>
     applies to the two remaining properties: <a href="#propdef-font-style"
     title="font-style!!property">‘<code
     class=property>font-style</code>’</a> and <a
     href="#propdef-font-weight" title="font-weight!!property">‘<code
     class=property>font-weight</code>’</a>.
    <p>The sixth rule sets the <a href="#propdef-font-style"
     title="font-style!!property">‘<code
     class=property>font-style</code>’</a>, <a href="#propdef-font-stretch"
     title="font-stretch!!property">‘<code
     class=property>font-stretch</code>’</a>, <span class=property>‘<a
     href="#propdef-font-size"><code
     class=property>font-size</code></a>’</span>, and <a
     href="#propdef-font-family" title="font-family!!property">‘<code
     class=property>font-family</code>’</a>, the other font properties being
     set to their initial values.
   </div>
   <p>Since the <a href="#propdef-font-stretch"
    title="font-stretch!!property">‘<code
    class=property>font-stretch</code>’</a> property was not defined in CSS
 .1, when using <a href="#propdef-font-stretch"
    title="font-stretch!!property">‘<code
    class=property>font-stretch</code>’</a> values within ‘<a
    href="#propdef-font"><code class=property>font</code></a>’ rules,
    authors should include a extra version compatible with older user agents:
   <pre>p {
   font: 80% sans-serif;   /* for older user agents */
   font: condensed 80% sans-serif;
 }</pre>
   <p>The following values refer to system fonts:
   <dl>
    <dt><strong>caption</strong>
    <dd>The font used for captioned controls (e.g., buttons, drop-downs,
     etc.).
    <dt><strong>icon</strong>
    <dd>The font used to label icons.
    <dt><strong>menu</strong>
    <dd>The font used in menus (e.g., dropdown menus and menu lists).
    <dt><strong>message-box</strong>
    <dd>The font used in dialog boxes.
    <dt><strong>small-caption</strong>
    <dd>The font used for labeling small controls.
    <dt><strong>status-bar</strong>
    <dd>The font used in window status bars.
   </dl>
   <p>System fonts may only be set as a whole; that is, the font family, size,
    weight, style, etc. are all set at the same time. These values may then be
    altered individually if desired. If no font with the indicated
    characteristics exists on a given platform, the user agent should either
    intelligently substitute (e.g., a smaller version of the ‘<code
    class=property>caption</code>’ font might be used for the ‘<code
    class=property>small-caption</code>’ font), or substitute a user agent
    default font. As for regular fonts, if, for a system font, any of the
    individual properties are not part of the operating system's available
    user preferences, those properties should be set to their initial values.
   <p>That is why this property is "almost" a shorthand property: system fonts
    can only be specified with this property, not with <a
    href="#propdef-font-family" title="font-family!!property">‘<code
    class=property>font-family</code>’</a> itself, so <span
    class=property>‘<a href="#propdef-font"><code
    class=property>font</code></a>’</span> allows authors to do more than
    the sum of its subproperties. However, the individual properties such as
    <a href="#propdef-font-weight" title="font-weight!!property">‘<code
    class=property>font-weight</code>’</a> are still given values taken from
    the system font, which can be independently varied.
   <p>Note that the keywords used for the system fonts listed above are only
    treated as keywords when they occur in the initial position, in other
    positions the same string is treated as part of the font family name:
   <pre>  font: menu;        /* use the font settings for system menus */
   font: large menu;  /* use a font family named "menu" */</pre>
   <div class=example>
    <p style="display:none">Example(s):</p>
    <pre>button { font: 300 italic 1.3em/1.7em &quot;FB Armada&quot;, sans-serif }
 button p { font: menu }
 button p em { font-weight: bolder }
 </pre>
    <p>If the font used for dropdown menus on a particular system happened to
     be, for example, 9-point Charcoal, with a weight of 600, then P elements
     that were descendants of BUTTON would be displayed as if this rule were
     in effect:
    <pre>button p { font: 600 9pt Charcoal }
 </pre>
    <p>Because the <span class=property>‘<a href="#propdef-font"><code
     class=property>font</code></a>’</span> shorthand resets to its initial
     value any property not explicitly given a value, this has the same effect
     as this declaration:
    <pre>button p {
   font-style: normal;
   font-variant: normal;
   font-weight: 600;
   font-size: 9pt;
   line-height: normal;
   font-family: Charcoal
 }
 </pre>
   </div>
   <!-- prop: font-synthesis -->
   <h3 id=font-synthesis-prop><span class=secno>3.8 </span>Controlling
    synthetic faces: the <a href="#propdef-font-synthesis">font-synthesis</a>
    property</h3>
   <table class=propdef id=namefont-synthesisvaluenone-weight-style>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-synthesis>font-synthesis</dfn>
     <tr>
      <td>Value:
      <td>none | [ weight || style ]
     <tr>
      <td>Initial:
      <td>weight style
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>This property controls whether user agents are allowed to synthesize
    bold or oblique font faces when a font family lacks bold or italic faces.
    If ‘<a href="#weight"><code class=property>weight</code></a>’ is not
    specified, user agents must not synthesize bold faces and if ‘<code
    class=property>style</code>’ is not specified user agents must not
    synthesize italic faces. A value of ‘<code class=property>none</code>’
    disallows all synthetic faces.
   <div class=example>
    <p>The style rule below disables the use of synthetically obliqued Arabic:</p>
    <pre>*:lang(ar) { font-synthesis: none; }
 </pre>
   </div>
   <h2 id=font-resources><span class=secno>4 </span>Font Resources</h2>
   <h3 id=font-face-rule><span class=secno>4.1 </span>The <dfn
    id=at-font-face-rule style="font-weight: inherit; font-style:
    inherit"><code>@font-face</code></dfn> rule</h3>
   <p>The <a href="#at-font-face-rule"><code>@font-face</code></a> rule allows
    for linking to fonts that are automatically fetched and activated when
    needed. This allows authors to select a font that closely matches the
    design goals for a given page rather than limiting the font choice to a
    set of fonts available on all platforms. A set of font descriptors define
    the location of a font resource, either locally or externally, along with
    the style characteristics of an individual face. Multiple <a
    href="#at-font-face-rule"><code>@font-face</code></a> rules can be used to
    construct font families with a variety of faces. Using CSS font matching
    rules, a user agent can selectively download only those faces that are
    needed for a given piece of text.
   <p>The <a href="#at-font-face-rule"><code>@font-face</code></a> rule
    consists of the <a href="#at-font-face-rule"><code>@font-face</code></a>
    at-keyword followed by a block of descriptor declarations. In terms of the
    grammar, this specification defines the following productions:
   <pre><dfn id=fontfacerule>font_face_rule</dfn>
   : <a href="#fontfacesym"><i>FONT_FACE_SYM</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* '{' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#descriptordeclaration"><i>descriptor_declaration</i></a>? [ ';' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#descriptordeclaration"><i>descriptor_declaration</i></a>? ]* '}' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
   ;
 <dfn id=descriptordeclaration>descriptor_declaration</dfn>
   : <a href="http://www.w3.org/TR/CSS21/grammar.html#grammar"><i>property</i></a> ':' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/grammar.html#grammar"><i>expr</i></a>
   ;</pre>
   <p>The following new definitions are introduced:
   <pre>-    -|\\0{0,4}2d(\r\n|[ \t\r\n\f])?
 F    f|\\0{0,4}(46|66)(\r\n|[ \t\r\n\f])?</pre>
   <p>The following new token is introduced:
   <pre>@{F}{O}{N}{T}{-}{F}{A}{C}{E} {return <dfn id=fontfacesym>FONT_FACE_SYM</dfn>;}</pre>
   <p>Each <a href="#at-font-face-rule"><code>@font-face</code></a> rule
    specifies a value for every font descriptor, either implicitly or
    explicitly. Those not given explicit values in the rule take the initial
    value listed with each descriptor in this specification. These descriptors
    apply solely within the context of the <a
    href="#at-font-face-rule"><code>@font-face</code></a> rule in which they
    are defined, and do not apply to document language elements. There is no
    notion of which elements the descriptors apply to or whether the values
    are inherited by child elements. When a given descriptor occurs multiple
    times in a given <a href="#at-font-face-rule"><code>@font-face</code></a>
    rule, only the last descriptor declaration is used and all prior
    declarations for that descriptor are ignored.
   <div class=example>
    <p>To use a downloadable font called Gentium:</p>
    <pre>
 @font-face {
   font-family: Gentium;
   src: url(http://example.com/fonts/Gentium.woff);
 }
 p { font-family: Gentium, serif; }
 </pre>
    <p>The user agent will download Gentium and use it when rendering text
     within paragraph elements. If for some reason the site serving the font
     is unavailable, the default serif font will be used.</p>
   </div>
   <p>A given set of <a href="#at-font-face-rule"><code>@font-face</code></a>
    rules define a set of fonts available for use within the documents that
    contain these rules. When font matching is done, fonts defined using these
    rules are considered before other available fonts on a system.
   <p>Downloaded fonts are only available to documents that reference them.
    The process of activating these fonts must not make them available to
    other applications or to documents that don't directly link to the same
    font. User agent implementers might consider it convenient to use
    downloaded fonts when rendering characters in other documents for which no
    other available font exists as part of the <a
    href="#system-font-fallback"><em>system font fallback</em></a> procedure.
    However, this would cause a security leak since the contents of one page
    would be able to affect other pages, something an attacker could use as an
    attack vector. These restrictions do not affect caching behavior, fonts
    are cached the same way other web resources are cached.
   <p>This at-rule follows the forward-compatible parsing rules of CSS. Like
    properties in a declaration block, declarations of any descriptors that
    are not supported by the user agent must be ignored. <a
    href="#at-font-face-rule"><code>@font-face</code></a> rules require a
    font-family and src descriptor; if either of these are missing, the <a
    href="#at-font-face-rule"><code>@font-face</code></a> rule is invalid and
    must be ignored entirely.
   <p>In cases where user agents have limited platform resources or implement
    the ability to disable downloadable font resources, <a
    href="#at-font-face-rule"><code>@font-face</code></a> rules must simply be
    ignored; the behavior of individual descriptors as defined in this
    specification should not be altered.
   <h3 id=font-family-desc><span class=secno>4.2 </span>Font family: the <a
    href="#descdef-font-family">font-family</a> descriptor</h3>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-family
       title="font-family!!descriptor">font-family</dfn>
     <tr>
      <td>Value:
      <td><a href="#family-name-value"><var>&lt;family-name&gt;</var></a>
     <tr>
      <td><em>Initial:</em>
      <td>N/A
   </table>
   <p>This descriptor defines the font family name that will be used in all
    CSS font family name matching. It is required for the <a
    href="#at-font-face-rule"><code>@font-face</code></a> rule to be valid. It
    overrides the font family names contained in the underlying font data. If
    the font family name is the same as a font family available in a given
    user's environment, it effectively hides the underlying font for documents
    that use the stylesheet. This permits a web author to freely choose
    font-family names without worrying about conflicts with font family names
    present in a given user's environment. Likewise, platform substitutions
    for a given font family name must not be used.
   <h3 id=src-desc><span class=secno>4.3 </span>Font reference: the <a
    href="#descdef-src">src</a> descriptor</h3>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-src>src</dfn>
     <tr>
      <td>Value:
      <td>[ &lt;url> [format(&lt;string> #)]? | <a
       href="#font-face-name-value"><var>&lt;font-face-name&gt;</var></a> ] #
     <tr>
      <td><em>Initial:</em>
      <td>N/A
   </table>
   <p>This descriptor specifies the resource containing font data. It is
    required for the <a href="#at-font-face-rule"><code>@font-face</code></a>
    rule to be valid. Its value is a prioritized, comma-separated list of
    external references or locally-installed font face names. When a font is
    needed the user agent iterates over the set of references listed, using
    the first one it can successfully activate. Fonts containing invalid data
    or local font faces that are not found are ignored and the user agent
    loads the next font in the list.
   <p>As with other URLs in CSS, the URL may be relative, in which case it is
    resolved relative to the location of the style sheet containing the <a
    href="#at-font-face-rule"><code>@font-face</code></a> rule. In the case of
    SVG fonts, the URL points to an element within a document containing SVG
    font definitions. If the element reference is omitted, a reference to the
    first defined font is implied. Similarly, font container formats that can
    contain more than one font must load one and only one of the fonts for a
    given <a href="#at-font-face-rule"><code>@font-face</code></a> rule.
    Fragment identifiers are used to indicate which font to load. If a
    container format lacks a defined fragment identifier scheme,
    implementations should use a simple 1-based indexing scheme (e.g.
    "font-collection#1" for the first font, "font-collection#2" for the second
    font).
   <pre>
 src: url(fonts/simple.woff);   /* load simple.woff relative to stylesheet location */
 src: url(/fonts/simple.woff);  /* load simple.woff from absolute location */
 src: url(fonts.svg#simple);    /* load SVG font with id 'simple' */
 </pre>
   <p>External references consist of a URL, followed by an optional hint
    describing the format of the font resource referenced by that URL. The
    format hint contains a comma-separated list of format strings that denote
    well-known font formats. Conformant user agents must skip downloading a
    font resource if the format hints indicate only unsupported or unknown
    font formats. If no format hints are supplied, the user agent should
    download the font resource.
   <pre>
 /* load WOFF font if possible, otherwise use OpenType font */
 @font-face {
   font-family: bodytext;
   src: url(ideal-sans-serif.woff) format("woff"),
        url(basic-sans-serif.ttf) format("opentype");
 }
 </pre>
   <p>Format strings defined by this specification:
   <table class=data id=fontformats>
    <thead>
     <tr>
      <th>String
      <th>Font Format
      <th>Common extensions
    <tbody>
     <tr>
      <th>"woff"
      <td><a href="http://www.w3.org/TR/WOFF/">WOFF (Web Open Font Format)</a>
      <td>.woff
     <tr>
      <th>"truetype"
      <td><a
       href="http://www.microsoft.com/typography/otspec/default.htm">TrueType</a>
      <td>.ttf
     <tr>
      <th>"opentype"
      <td><a
       href="http://www.microsoft.com/typography/otspec/default.htm">OpenType</a>
      <td>.ttf, .otf
     <tr>
      <th>"embedded-opentype"
      <td><a
       href="http://www.w3.org/Submission/2008/SUBM-EOT-20080305/">Embedded
       OpenType</a>
      <td>.eot
     <tr>
      <th>"svg"
      <td><a href="http://www.w3.org/TR/SVG/fonts.html">SVG Font</a>
      <td>.svg, .svgz
   </table>
   <p>Given the overlap in common usage between TrueType and OpenType, the
    format hints "truetype" and "opentype" must be considered as synonymous; a
    format hint of "opentype" does not imply that the font contains Postscript
    CFF style glyph data or that it contains OpenType layout information (see
    <a href="#platform-props-to-css">Appendix A</a> for more background on
    this).
   <p>When authors would prefer to use a locally available copy of a given
    font and download it if it's not, <code>local()</code> can be used. The
    locally-installed <dfn
    id=font-face-name-value><var>&lt;font-face-name&gt;</var></dfn> argument
    to <code>local()</code> is a format-specific string that uniquely
    identifies a single font face within a larger family. The syntax for a <a
    href="#font-face-name-value"><var>&lt;font-face-name&gt;</var></a> is a
    unique font face name enclosed by "local(" and ")". The name can
    optionally be enclosed in quotes. If unquoted, the unquoted font family
    name processing conventions apply; the name must be a sequence of
    identifiers separated by whitespace which is converted to a string by
    joining the identifiers together separated by a single space.
   <pre>
 /* regular face of Gentium */
 @font-face {
   font-family: MyGentium;
   src: local(Gentium),    /* use locally available Gentium */
        url(Gentium.woff); /* otherwise, download it */
 }
 </pre>
   <p>For OpenType and TrueType fonts, this string is used to match only the
    Postscript name or the full font name in the name table of locally
    available fonts. Which type of name is used varies by platform and font,
    so authors should include both of these names to assure proper matching
    across platforms. Platform substitutions for a given font name must not be
    used.
   <pre>
 /* bold face of Gentium */
 @font-face {
   font-family: MyGentium;
   src: local(Gentium Bold),    /* full font name */
        local(Gentium-Bold),    /* Postscript name */
        url(GentiumBold.woff);  /* otherwise, download it */
   font-weight: bold;
 }
 </pre>
   <p>Just as a <a href="#at-font-face-rule"><code>@font-face</code></a> rule
    specifies the characteristics of a single font within a family, the unique
    name used with <code>local()</code> specifies a single font, not an entire
    font family. Defined in terms of OpenType font data, the Postscript name
    is found in the font's <a
    href="http://www.microsoft.com/typography/otspec/name.htm">name table</a>,
    in the name record with nameID = 6 (see <a href="#OPENTYPE"
    rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a> for more details). The
    Postscript name is the commonly used key for all fonts on OSX and for
    Postscript CFF fonts under Windows. The full font name (nameID = 4) is
    used as a unique key for fonts with TrueType glyphs on Windows.
   <p>For OpenType fonts with multiple localizations of the full font name,
    the US English version is used (language ID = 0x409 for Windows and
    language ID = 0 for Macintosh) or the first localization when a US English
    full font name is not available (the OpenType specification recommends
    that <a href="http://www.microsoft.com/typography/otspec/recom.htm">all
    fonts minimally include US English names</a>). User agents that also match
    other full font names, e.g. matching the Dutch name when the current
    system locale is set to Dutch, are considered non-conformant. This is done
    not to prefer English but to avoid matching inconsistencies across font
    versions and OS localizations, since font style names (e.g. "Bold") are
    frequently localized into many languages and the set of localizations
    available varies widely across platform and font version. User agents that
    match a concatenation of family name (nameID = 1) with style name (nameID
    = 2) are considered non-conformant.
   <p>This also allows for referencing faces that belong to larger families
    that cannot otherwise be referenced.
   <div class=example>
    <p>Use a local font or reference an SVG font in another document:</p>
    <pre>
 @font-face {
   font-family: Headline;
   src: local(Futura-Medium),
        url(fonts.svg#MyGeometricModern) format("svg");
 }
 </pre>
    <p>Create an alias for local Japanese fonts on different platforms:</p>
    <pre>
 @font-face {
   font-family: jpgothic;
   src: local(HiraKakuPro-W3), local(Meiryo), local(IPAPGothic);
 }
 </pre>
    <p>Reference a font face that cannot be matched within a larger family:</p>
    <pre>
 @font-face {
   font-family: Hoefler Text Ornaments;
   /* has the same font properties as Hoefler Text Regular */
   src: local(HoeflerText-Ornaments);
 }
 </pre>
    <p>Since localized fullnames never match, a document with the header style
     rules below would always render using the default serif font, regardless
     whether a particular system locale parameter is set to Finnish or not:</p>
    <pre>
 @font-face {
   font-family: SectionHeader;
   src: local("Arial Lihavoitu");  /* Finnish fullname for Arial Bold, should fail */
   font-weight: bold;
 }
 h2 { font-family: SectionHeader, serif; }
 </pre>
    <p>A conformant user agent would never load the font ‘<code
     class=css>gentium.eot</code>’ in the example below, since it is
     included in the first definition of the ‘<a href="#descdef-src"><code
     class=property>src</code></a>’ descriptor which is overridden by the
     second definition in the same <a
     href="#at-font-face-rule"><code>@font-face</code></a> rule:</p>
    <pre>
 @font-face {
   font-family: MainText;
   src: url(gentium.eot);                     /* for use with older user agents */
   src: local("Gentium"), url(gentium.woff);  /* Overrides src definition */
 }
 </pre>
   </div>
   <h3 id=font-prop-desc><span class=secno>4.4 </span>Font property
    descriptors: the <a href="#descdef-font-style">font-style</a>, <a
    href="#descdef-font-weight">font-weight</a>, <a
    href="#descdef-font-stretch">font-stretch</a> descriptors</h3>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-style
       title="font-style!!descriptor">font-style</dfn>
     <tr>
      <td>Value:
      <td>normal | italic | oblique
     <tr>
      <td><em>Initial:</em>
      <td>normal
   </table>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-weight
       title="font-weight!!descriptor">font-weight</dfn>
     <tr>
      <td>Value:
      <td>normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
     <tr>
      <td><em>Initial:</em>
      <td>normal
   </table>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-stretch
       title="font-stretch!!descriptor">font-stretch</dfn>
     <tr>
      <td>Value:
      <td>normal | ultra-condensed | extra-condensed | condensed |
       semi-condensed | semi-expanded | expanded | extra-expanded |
       ultra-expanded
     <tr>
      <td><em>Initial:</em>
      <td>normal
   </table>
   <p>These descriptors define the characteristics of a font face and are used
    in the process of matching styles to specific faces. For a font family
    defined with several <a
    href="#at-font-face-rule"><code>@font-face</code></a> rules, user agents
    can either download all faces in the family or use these descriptors to
    selectively download font faces that match actual styles used in document.
    The values for these descriptors are the same as those for the
    corresponding font properties except that relative keywords are not
    allowed, ‘<a href="#bolder"><code class=property>bolder</code></a>’
    and ‘<a href="#lighter"><code class=property>lighter</code></a>’. If
    these descriptors are omitted, initial values are assumed.
   <p>The value for these font face style attributes is used in place of the
    style implied by the underlying font data. This allows authors to combine
    faces in flexible combinations, even in situations where the original font
    data was arranged differently. User agents that implement synthetic
    bolding and obliquing must only apply synthetic styling in cases where the
    font descriptors imply this is needed, rather than based on the style
    attributes implied by the font data.
   <h3 id=unicode-range-desc><span class=secno>4.5 </span>Character range: the
    <a href="#descdef-unicode-range">unicode-range</a> descriptor</h3>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-unicode-range>unicode-range</dfn>
     <tr>
      <td>Value:
      <td><a href="#urange-value"><var>&lt;urange&gt;</var></a> #
     <tr>
      <td><em>Initial:</em>
      <td>U+0-10FFFF
   </table>
   <p>This descriptor defines the set of Unicode codepoints that may be
    supported by the font face for which it is declared. The descriptor value
    is a comma-delimited list of Unicode range (<a
    href="#urange-value"><var>&lt;urange&gt;</var></a>) values. The union of
    these ranges defines the set of codepoints that serves as a hint for user
    agents when deciding whether or not to download a font resource for a
    given text run.
   <p>Each <dfn id=urange-value><var>&lt;urange&gt;</var></dfn> value is a <a
    href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><code
    title="UNICODE-RANGE token">UNICODE-RANGE</code></a> token made up of a
    "U+" or "u+" prefix followed by a codepoint range in one of the three
    forms listed below. Ranges that do not fit one of the these forms are
    invalid and cause the declaration to be ignored.
   <dl>
    <dt>single codepoint (e.g. U+416)
    <dd>a valid Unicode codepoint, represented as one to six hexadecimal
     digits
    <dt>interval range (e.g. U+400-4ff)
    <dd>represented as two hyphen-separated valid Unicode codepoints
     indicating the inclusive start and end codepoints of a range
    <dt>wildcard range (e.g. U+4??)
    <dd>defined by the set of codepoints implied when trailing ‘<code
     class=css>?</code>’ characters signify any hexadeximal digit
   </dl>
   <p>Individual codepoints are written using hexadecimal values that
    correspond to <a href="http://www.unicode.org/charts/">Unicode character
    codepoints</a>. Valid Unicode codepoint values vary between 0 and 10FFFF
    inclusive. Digit values of codepoints are ASCII case-insensitive. For
    interval ranges, the start and end codepoints are valid Unicode values and
    the end codepoint is greater than or equal to the start codepoint.
   <p>Wildcard ranges specified with ‘?’ that lack an initial digit (e.g.
    "U+???") are valid and equivalent to a wildcard range with an initial zero
    digit (e.g. "U+0???" = "U+0000-0FFF"). Wildcard ranges that extend beyond
    the range of valid Unicode codepoints are invalid. Because of this, the
    maximum number of trailing ‘<code class=css>?</code>’ wildcard
    characters is five, even though the <a
    href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><code
    title="UNICODE-RANGE token">UNICODE-RANGE</code></a> token accepts six.
   <p>Within the comma-delimited list of Unicode ranges in a ‘<a
    href="#descdef-unicode-range"><code
    class=property>unicode-range</code></a>’ descriptor declaration, ranges
    may overlap. The union of these ranges defines the set of codepoints for
    which the corresponding font may be used. User agents must not download or
    use the font for codepoints outside this set. User agents may normalize
    the list of ranges into a list that is different but represents the same
    set of codepoints.
   <p>The associated font might not contain glyphs for the entire set of
    codepoints defined by the ‘<a href="#descdef-unicode-range"><code
    class=property>unicode-range</code></a>’ descriptor. When the font is
    used, the <dfn id=effective-character-map>effective character map</dfn> is
    the intersection of the codepoints defined by ‘<a
    href="#descdef-unicode-range"><code
    class=property>unicode-range</code></a>’ with the font's <a
    href="#character-map"><em>character map</em></a>. This allows authors to
    define supported ranges in terms of broad ranges without worrying about
    the precise codepoint ranges supported by the underlying font.
   <h3 id=composite-fonts><span class=secno>4.6 </span>Using character ranges
    to define composite fonts</h3>
   <p>Multiple <a href="#at-font-face-rule"><code>@font-face</code></a> rules
    with different unicode ranges for the same family and style descriptor
    values can be used to create composite fonts that mix the glyphs from
    different fonts for different scripts. This can be used to combine fonts
    that only contain glyphs for a single script (e.g. Latin, Greek, Cyrillic)
    or it can be used by authors as a way of segmenting a font into fonts for
    commonly used characters and less frequently used characters. Since the
    user agent will only pull down the fonts it needs this helps reduce page
    bandwidth.
   <p>If the unicode ranges overlap for a set of <a
    href="#at-font-face-rule"><code>@font-face</code></a> rules with the same
    family and style descriptor values, the rules are ordered in the reverse
    order they were defined; the last rule defined is the first to be checked
    for a given character.
   <p>Example ranges for specific languages or characters:
   <dl>
    <dt>unicode-range: U+A5;
    <dd>a single code point, the yen/yuan symbol
    <dt>unicode-range: U+0-7F;
    <dd>code range for basic ASCII characters
    <dt>unicode-range: U+590-5ff;
    <dd>code range for Hebrew characters
    <dt>unicode-range: U+A5, U+4E00-9FFF, U+30??, U+FF00-FF9F;
    <dd>code range for Japanese kanji, hiragana and katakana characters plus
     yen/yuan symbol
   </dl>
   <div class=example>
    <p>The BBC provides news services in a wide variety of languages, many
     that are not well supported across all platforms. Using an <a
     href="#at-font-face-rule"><code>@font-face</code></a> rule, the BBC could
     provide a font for any of these languages, as it already does via a
     manual font download.</p>
    <pre>
 @font-face {
   font-family: BBCBengali;
   src: url(fonts/BBCBengali.woff) format("woff");
   unicode-range: U+00-FF, U+980-9FF;
 }
 </pre>
   </div>
   <div class=example>
    <p>Technical documents often require a wide range of symbols. The STIX
     Fonts project is one project aimed at providing fonts to support a wide
     range of technical typesetting in a standardized way. The example below
     shows the use of a font that provides glyphs for many of the mathematical
     and technical symbol ranges within Unicode:</p>
    <pre>
 @font-face {
   font-family: STIXGeneral;
   src: local(STIXGeneral), url(/stixfonts/STIXGeneral.otf);
   unicode-range: U+000-49F, U+2000-27FF, U+2900-2BFF, U+1D400-1D7FF;
 }
 </pre>
   </div>
   <div class=example>
    <p>This example shows how an author can override the glyphs used for Latin
     characters in a Japanese font with glyphs from a different font. The
     first rule specifies no range so it defaults to the entire range. The
     range specified in the second rule overlaps but takes precedence because
     it is defined later.</p>
    <pre>
 @font-face {
   font-family: JapaneseWithGentium;
   src: local(MSMincho);
   /* no range specified, defaults to entire range */
 }
 @font-face {
   font-family: JapaneseWithGentium;
   src: url(../fonts/Gentium.woff);
   unicode-range: U+0-2FF;
 }
 </pre>
   </div>
   <div class=example>
    <p>Consider a family constructed to optimize bandwidth by separating out
     Latin, Japanese and other characters into different font files:</p>
    <pre>
 /* fallback font - size: 4.5MB */
 @font-face {
   font-family: DroidSans;
   src: url(DroidSansFallback.woff);
   /* no range specified, defaults to entire range */
 }
 /* Japanese glyphs - size: 1.2MB */
 @font-face {
   font-family: DroidSans;
   src: url(DroidSansJapanese.woff);
   unicode-range: U+3000-9FFF, U+ff??;
 }
 /* Latin, Greek, Cyrillic along with some
    punctuation and symbols - size: 190KB */
 @font-face {
   font-family: DroidSans;
   src: url(DroidSans.woff);
   unicode-range: U+000-5FF, U+1e00-1fff, U+2000-2300;
 }
 </pre>
    <p>For simple Latin text, only the font for Latin characters is
     downloaded:</p>
    <pre>
 body { font-family: DroidSans; }
 &lt;p>This is that&lt;/p>
 </pre>
    <p>In this case the user agent first checks the unicode-range for the font
     containing Latin characters (DroidSans.woff). Since all the characters
     above are in the range U+0-5FF, the user agent downloads the font and
     renders the text with that font.</p>
    <p>Next, consider text that makes use of an arrow character (⇨):</p>
    <pre>
 &lt;p>This &amp;#x21e8; that&lt;p>
 </pre>
    <p>The user agent again first checks the unicode-range of the font
     containing Latin characters. Since U+2000-2300 includes the arrow code
     point (U+21E8), the user agent downloads the font. For this character
     however the Latin font does not have a matching glyph, so the effective
     unicode-range used for font matching excludes this code point. Next, the
     user agent evaluates the Japanese font. The unicode-range for the
     Japanese font, U+3000-9FFF and U+ff??, does not include U+21E8, so the
     user agent does not download the Japanese font. Next the fallback font is
     considered. The <a href="#at-font-face-rule"><code>@font-face</code></a>
     rule for the fallback font does not define unicode-range so its value
     defaults to the range of all Unicode code points. The fallback font is
     downloaded and used to render the arrow character.</p>
   </div>
   <h3 id=font-rend-desc><span class=secno>4.7 </span>Font features: the <a
    href="#descdef-font-variant">font-variant</a> and <a
    href="#descdef-font-feature-settings">font-feature-settings</a>
    descriptors</h3>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-variant
       title="font-variant!!descriptor">font-variant</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-variant-normal-value"
       title="normal!!font-variant">normal</a> | <a
       href="#font-variant-none-value" title="none!!font-variant">none</a> | [
       <a href="#common-lig-values"><var>&lt;common-lig-values&gt;</var></a>
       || <a
       href="#discretionary-lig-values"><var>&lt;discretionary-lig-values&gt;</var></a>
       || <a
       href="#historical-lig-values"><var>&lt;historical-lig-values&gt;</var></a>
       || <a
       href="#contextual-alt-values"><var>&lt;contextual-alt-values&gt;</var></a>
       || <a href="#stylistic"><var
       title=stylistic>stylistic(&lt;feature-value-name&gt;)</var></a> || <a
       href="#historical-forms"><var>historical-forms</var></a> || <a
       href="#styleset"><var
       title=styleset>styleset(&lt;feature-value-name&gt; #)</var></a> || <a
       href="#character-variant"><var
       title=character-variant>character-variant(&lt;feature-value-name&gt;
       #)</var></a> || <a href="#swash"><var
       title=swash>swash(&lt;feature-value-name&gt;)</var></a> || <a
       href="#ornaments"><var
       title=ornaments>ornaments(&lt;feature-value-name&gt;)</var></a> || <a
       href="#annotation"><var
       title=annotation>annotation(&lt;feature-value-name&gt;)</var></a> || [
       <a href="#small-caps"><i>small-caps</i></a> | <a
       href="#all-small-caps"><i>all-small-caps</i></a> | <a
       href="#petite-caps"><i>petite-caps</i></a> | <a
       href="#all-petite-caps"><i>all-petite-caps</i></a> | <a
       href="#unicase"><i>unicase</i></a> | <a
       href="#titling-caps"><i>titling-caps</i></a> ] || <a
       href="#numeric-figure-values"><var>&lt;numeric-figure-values&gt;</var></a>
       || <a
       href="#numeric-spacing-values"><var>&lt;numeric-spacing-values&gt;</var></a>
       || <a
       href="#numeric-fraction-values"><var>&lt;numeric-fraction-values&gt;</var></a>
       || <a href="#ordinal"><i>ordinal</i></a> || <a
       href="#slashed-zero"><i>slashed-zero</i></a> || <a
       href="#east-asian-variant-values"><var>&lt;east-asian-variant-values&gt;</var></a>
       || <a
       href="#east-asian-width-values"><var>&lt;east-asian-width-values&gt;</var></a>
       || <a href="#ruby"><i>ruby</i></a> ]
     <tr>
      <td><em>Initial:</em>
      <td>normal
   </table>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-feature-settings
       title="font-feature-settings!!descriptor">font-feature-settings</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-feature-settings-normal-value"
       title="normal!!font-feature-settings">normal</a> | <a
       href="#feature-tag-value"><var>&lt;feature-tag-value&gt;</var></a> #
     <tr>
      <td><em>Initial:</em>
      <td>normal
   </table>
   <p>These descriptors define initial settings that apply when the font
    defined by an <a href="#at-font-face-rule"><code>@font-face</code></a>
    rule is rendered. They do not affect font selection. Values are identical
    to those defined for the corresponding <a href="#propdef-font-variant"
    title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> and <a
    href="#propdef-font-feature-settings"
    title="font-feature-settings!!property">‘<code
    class=property>font-feature-settings</code>’</a> properties defined
    below except that the value ‘<code class=property>inherit</code>’ is
    omitted. When multiple font feature descriptors or properties are used,
    the cumulative effect on text rendering is detailed in the section <a
    href="#font-feature-resolution">Font Feature Resolution</a> below. In
    cases where specific values define synthesized fallback for certain <a
    href="#propdef-font-variant" title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> subproperties, the same
    synthesized fallback applies when used within those values are used with
    the <a href="#descdef-font-style" title="font-style!!descriptor">‘<code
    class=property>font-variant</code>’</a> descriptor.
   <h3 id=font-face-loading><span class=secno>4.8 </span>Font loading
    guidelines</h3>
   <p>The <a href="#at-font-face-rule"><code>@font-face</code></a> rule is
    designed to allow lazy loading of font resources that are only downloaded
    when used within a document. A stylesheet can include <a
    href="#at-font-face-rule"><code>@font-face</code></a> rules for a library
    of fonts of which only a select set are used; user agents must only
    download those fonts that are referred to within the style rules
    applicable to a given page. User agents that download all fonts defined in
    <a href="#at-font-face-rule"><code>@font-face</code></a> rules without
    considering whether those fonts are in fact used within a page are
    considered non-conformant. In cases where a font might be downloaded in
    character fallback cases, user agents may download a font if it's
    contained within the computed value of <a href="#propdef-font-family"
    title="font-family!!property">‘<code
    class=property>font-family</code>’</a> for a given text run.
   <pre>
 @font-face {
   font-family: GeometricModern;
   src: url(font.woff);
 }
 p {
   /* font will be downloaded for pages with p elements */
   font-family: GeometricModern, sans-serif;
 }
 h2 {
   /* font may be downloaded for pages with h2 elements, even if Futura is available locally */
   font-family: Futura, GeometricModern, sans-serif;
 }
 </pre>
   <p>In cases where textual content is loaded before downloadable fonts are
    available, user agents may render text as it would be rendered if
    downloadable font resources are not available or they may render text
    transparently with fallback fonts to avoid a flash of text using a
    fallback font. In cases where the font download fails user agents must
    display text, simply leaving transparent text is considered non-conformant
    behavior. Authors are advised to use fallback fonts in their font lists
    that closely match the metrics of the downloadable fonts to avoid large
    page reflows where possible.
   <p><a id=same-origin-restriction> </a><a
    id=allowing-cross-origin-font-loading> </a>
   <h3 id=font-fetching-requirements><span class=secno>4.9 </span>Font
    fetching requirements</h3>
   <!-- TPAC 2011 Resolution to require same-origin restriction for loading fonts:
   http://lists.w3.org/Archives/Public/www-style/2011Nov/0711.html
   http://www.w3.org/2011/10/31-webapps-minutes.html#item02
 -->
   <p>For font loads, user agents must use the <a
    href="http://www.w3.org/TR/html5/infrastructure.html#cors-enabled-fetch">potentially
    CORS-enabled fetch</a> method defined by the <a href="#HTML5"
    rel=biblioentry>[HTML5]<!--{{!HTML5}}--></a> specification for URL's
    defined within @font-face rules. When fetching, user agents must use
    "Anonymous" mode, set the referrer source to the stylesheet's URL and set
    the origin to the URL of the containing document.
   <p class=note>The implications of this for authors are that fonts will
    typically not be loaded cross-origin unless authors specifically takes
    steps to permit cross-origin loads. Sites can explicitly allow cross-site
    loading of font data using the <code>Access-Control-Allow-Origin</code>
    HTTP header. For other schemes, no explicit mechanism to allow
    cross-origin loading, beyond what is permitted by the <a
    href="http://www.w3.org/TR/html5/infrastructure.html#cors-enabled-fetch">potentially
    CORS-enabled fetch</a> method, is defined or required.
   <div class=example> For the examples given below, assume that a document is
    located at <code>http://example.com/page.html</code> and all URL's link to
    valid font resources supported by the user agent. Fonts defined with the
    ‘<a href="#descdef-src"><code class=property>src</code></a>’
    descriptor values below will be loaded:
    <pre>/* same origin (i.e. domain, scheme, port match document) */
 src: url(fonts/simple.woff);
 src: url(//fonts/simple.woff);
 /* data url's with no redirects are treated as same origin */
 src: url("data:application/font-woff;base64,...");
 /* cross origin, different domain */
 /* Access-Control-Allow-Origin response header set to '*' */
 src: url(http://another.example.com/fonts/simple.woff);
 </pre>
    Fonts defined with the ‘<a href="#descdef-src"><code
    class=property>src</code></a>’ descriptor values below will fail to
    load:
    <pre>/* cross origin, different scheme */
 /* no Access-Control-xxx headers in response */
 src: url(https://example.com/fonts/simple.woff);
 /* cross origin, different domain */
 /* no Access-Control-xxx headers in response */
 src: url(http://another.example.com/fonts/simple.woff);
 </pre>
   </div>
   <h2 id=font-matching-algorithm><span class=secno>5 </span>Font Matching
    Algorithm</h2>
   <p>The algorithm below describes how fonts are associated with individual
    runs of text. For each character in the run a font family is chosen and a
    particular font face is selected containing a glyph for that character.
   <h3 id=font-family-casing><span class=secno>5.1 </span>Case sensitivity of
    font family names</h3>
   <p>As part of the font matching algorithm outlined below, user agents must
    match font family names used in style rules with actual font family names
    contained in fonts available in a given environment or with font family
    names defined in <a href="#at-font-face-rule"><code>@font-face</code></a>
    rules. User agents must match these names case insensitively, using the
    "Default Caseless Matching" algorithm outlined in the Unicode
    specification <a href="#UNICODE6"
    rel=biblioentry>[UNICODE6]<!--{{!UNICODE6}}--></a>. This algorithm is
    detailed in section 3.13 entitled "Default Case Algorithms". Specifically,
    the algorithm must be applied without normalizing the strings involved and
    without applying any language-specific tailorings. The case folding method
    specified by this algorithm uses the case mappings with status field
    ‘<code class=property>C</code>’ or ‘<code class=property>F</code>’
    in the CaseFolding.txt file of the Unicode Character Database.
   <p class=note> For authors this means that font family names are matched
    case insensitively, whether those names exist in a platform font or in the
    <a href="#at-font-face-rule"><code>@font-face</code></a> rules contained
    in a stylesheet. Authors should take care to ensure that names use a
    character sequence consistent with the actual font family name,
    particularly when using combining characters such as diacritical marks.
    For example, a family name that contains an uppercase A (U+0041) followed
    by a combining ring (U+030A) will <strong>not</strong> match a name that
    looks identical but which uses the precomposed lowercase a-ring character
    (U+00E5) instead of the combining sequence.
   <p class=note> Implementors should take care to verify that a given
    caseless string comparison implementation uses this precise algorithm and
    not assume that a given platform string matching routine follows it, as
    many of these have locale-specific behavior or use some level of string
    normalization.
   <h3 id=font-style-matching><span class=secno>5.2 </span>Matching font
    styles</h3>
   <p>The procedure for choosing a font for a given character in a run of text
    consists of iterating over the font families named by the <a
    href="#propdef-font-family" title="font-family!!property">‘<code
    class=property>font-family</code>’</a> property, selecting a font face
    with the appropriate style based on other font properties and then
    determining whether a glyph exists for the given character. This is done
    using the <dfn id=character-map>character map</dfn> of the font, data
    which maps characters to the default glyph for that character. A font is
    considered to <dfn id=support>support</dfn> a given character if (1) the
    character is contained in the font's <a
    href="#character-map"><em>character map</em></a> and (2) if required by
    the containing script, shaping information is available for that
    character.
   <p>Some legacy fonts may include a given character in the <a
    href="#character-map"><em>character map</em></a> but lack the shaping
    information (e.g. <a
    href="http://www.microsoft.com/typography/otspec/ttochap1.htm">OpenType
    layout tables</a> or <a
    href="http://scripts.sil.org/cms/scripts/page.php?site_id=projects&amp;item_id=graphite_techAbout">Graphite
    tables</a>) necessary for correctly rendering text runs containing that
    character.
   <p>Codepoint sequences consisting of a base character followed by a
    sequence of combining characters are treated slightly differently, see the
    section on <a href="#cluster-matching">cluster matching</a> below.
   <p>For this procedure, the <dfn id=default-face>default face</dfn> for a
    given font family is defined to be the face that would be selected if all
    font style properties were set to their initial value.
   <ol id=fontmatchingalg>
    <li>Using the computed font property values for a given element, the user
     agent starts with the first family name specified by the <a
     href="#propdef-font-family" title="font-family!!property">‘<code
     class=property>font-family</code>’</a> property.
    <li>If the family name is a generic family keyword, the user agent looks
     up the appropriate font family name to be used. User agents may choose
     the generic font family to use based on the language of the containing
     element or the Unicode range of the character.
    <li>For other family names, the user agent attempts to find the family
     name among fonts defined via <a
     href="#at-font-face-rule"><code>@font-face</code></a> rules and then
     among available system fonts, matching names with a <a
     href="#font-family-casing">case-insensitive comparison</a> as outlined in
     the section above. On systems containing fonts with multiple localized
     font family names, user agents must match any of these names independent
     of the underlying system locale or platform API used. If the font
     resources defined for a given face in an <a
     href="#at-font-face-rule"><code>@font-face</code></a> rule are either not
     available or contain invalid font data, then the face should be treated
     as not present in the family. If no faces are present for a family
     defined via <a href="#at-font-face-rule"><code>@font-face</code></a>
     rules, the family should be treated as missing; matching a platform font
     with the same name must not occur in this case.
    <li>If a font family match occurs, the user agent assembles the set of
     font faces in that family and then narrows the set to a single face using
     other font properties in the order given below. A group of faces defined
     via <a href="#at-font-face-rule"><code>@font-face</code></a> rules with
     identical font descriptor values but differing ‘<a
     href="#descdef-unicode-range"><code
     class=property>unicode-range</code></a>’ values are considered to be a
     single <dfn id=composite-face>composite face</dfn> for this step:
     <ol id=fontstylematchingalg>
      <li><a href="#propdef-font-stretch"
       title="font-stretch!!property">‘<code
       class=property>font-stretch</code>’</a> is tried first. If the
       matching set contains faces with width values matching the <a
       href="#propdef-font-stretch" title="font-stretch!!property">‘<code
       class=property>font-stretch</code>’</a> value, faces with other width
       values are removed from the matching set. If there is no face that
       exactly matches the width value the nearest width is used instead. If
       the value of <a href="#propdef-font-stretch"
       title="font-stretch!!property">‘<code
       class=property>font-stretch</code>’</a> is <a
       href="#font-stretch-normal-value" title="normal!!font-stretch">‘<code
       class=property>normal</code>’</a> or one of the condensed values,
       narrower width values are checked first, then wider values. If the
       value of <a href="#propdef-font-stretch"
       title="font-stretch!!property">‘<code
       class=property>font-stretch</code>’</a> is one of the expanded
       values, wider values are checked first, followed by narrower values.
       Once the closest matching width has been determined by this process,
       faces with other widths are removed from the matching set.
      <li><a href="#propdef-font-style" title="font-style!!property">‘<code
       class=property>font-style</code>’</a> is tried next. If the value of
       <a href="#propdef-font-style" title="font-style!!property">‘<code
       class=property>font-style</code>’</a> is ‘<a href="#italic"><code
       class=property>italic</code></a>’, italic faces are checked first,
       then oblique, then normal faces. If the value is ‘<a
       href="#oblique"><code class=property>oblique</code></a>’, oblique
       faces are checked first, then italic faces and then normal faces. If
       the value is <a href="#font-style-normal-value"
       title="normal!!font-style">‘<code
       class=property>normal</code>’</a>, normal faces are checked first,
       then oblique faces, then italic faces. Faces with other style values
       are excluded from the matching set. User agents are permitted to
       distinguish between italic and oblique faces within platform font
       families but this is not required, so all italic or oblique faces may
       be treated as italic faces. However, within font families defined via
       <a href="#at-font-face-rule"><code>@font-face</code></a> rules, italic
       and oblique faces must be distinguished using the value of the <a
       href="#descdef-font-style" title="font-style!!descriptor">‘<code
       class=property>font-style</code>’</a> descriptor. For families that
       lack any italic or oblique faces, users agents may create artificial
       oblique faces, if this is permitted by the value of the ‘<a
       href="#propdef-font-synthesis"><code
       class=property>font-synthesis</code></a>’ property.
      <li><a href="#propdef-font-weight"
       title="font-weight!!property">‘<code
       class=property>font-weight</code>’</a> is matched next, so it will
       always reduce the matching set to a single font face. If bolder/lighter
       relative weights are used, the effective weight is calculated based on
       the inherited weight value, as described in the definition of the <a
       href="#propdef-font-weight" title="font-weight!!property">‘<code
       class=property>font-weight</code>’</a> property. Given the desired
       weight and the weights of faces in the matching set after the steps
       above, if the desired weight is available that face matches. Otherwise,
       a weight is chosen using the rules below:
       <ul>
        <li>If the desired weight is less than 400, weights below the desired
         weight are checked in descending order followed by weights above the
         desired weight in ascending order until a match is found.
        <li>If the desired weight is greater than 500, weights above the
         desired weight are checked in ascending order followed by weights
         below the desired weight in descending order until a match is found.
        <li>If the desired weight is 400, 500 is checked first and then the
         rule for desired weights less than 400 is used.
        <li>If the desired weight is 500, 400 is checked first and then the
         rule for desired weights less than 400 is used.
       </ul>
      <li><span class=property>‘<a href="#propdef-font-size"><code
       class=property>font-size</code></a>’</span> must be matched within a
       UA-dependent margin of tolerance. (Typically, sizes for scalable fonts
       are rounded to the nearest whole pixel, while the tolerance for
       bitmapped fonts could be as large as 20%.) Further computations, e.g.,
       by ‘<code class=property>em</code>’ values in other properties, are
       based on the <span class=property>‘<a href="#propdef-font-size"><code
       class=property>font-size</code></a>’</span> value that is used, not
       the one that is specified.
     </ol>
    <li>
     <p>If the matched face is defined via <a
      href="#at-font-face-rule"><code>@font-face</code></a> rules, user agents
      must use the procedure below to select a single font:
     <ol>
      <li>If the font resource has not been loaded and the range of characters
       defined by the ‘<a href="#descdef-unicode-range"><code
       class=property>unicode-range</code></a>’ descriptor value includes
       the character in question, load the font.
      <li>After downloading, if the <a
       href="#effective-character-map"><em>effective character map</em></a>
       supports the character in question, select that font.
     </ol>
     <p>When the matched face is a <a href="#composite-face"><em>composite
      face</em></a>, user agents must use the procedure above on each of the
      faces in the <a href="#composite-face"><em>composite face</em></a> in
      reverse order of <a
      href="#at-font-face-rule"><code>@font-face</code></a> rule definition.</p>
     <p>While the download occurs, user agents may either wait until the font
      is downloaded or render once with substituted font metrics and render
      again once the font is downloaded.</p>
    <li>
     <p>If no matching face exists or the matched face does not contain a
      glyph for the character to be rendered, the next family name is selected
      and the previous three steps repeated. Glyphs from other faces in the
      family are not considered. The only exception is that user agents may
      optionally substitute a synthetically obliqued version of the <a
      href="#default-face"><em>default face</em></a> if that face supports a
      given glyph and synthesis of these faces is permitted by the value of
      the ‘<a href="#propdef-font-synthesis"><code
      class=property>font-synthesis</code></a>’ property. For example, a
      synthetic italic version of the regular face may be used if the italic
      face doesn't support glyphs for Arabic.</p>
     <!-- resolution on the above: http://lists.w3.org/Archives/Public/www-style/2012Nov/0292.html -->
    <li>If there are no more font families to be evaluated and no matching
     face has been found, then the user agent performs a <dfn
     id=system-font-fallback>system font fallback</dfn> procedure to find the
     best match for the character to be rendered. The result of this procedure
     may vary across user agents.
    <li>If a particular character cannot be displayed using any font, the user
     agent should indicate by some means that a character is not being
     displayed, displaying either a symbolic representation of the missing
     glyph (e.g. using a <a
     href="http://en.wikipedia.org/wiki/Last_resort_font">Last Resort
     Font</a>) or using the missing character glyph from a default font.
   </ol>
   <p>Optimizations of this process are allowed provided that an
    implementation behaves as if the algorithm had been followed exactly.
    Matching occurs in a well-defined order to insure that the results are as
    consistent as possible across user agents, given an identical set of
    available fonts and rendering technology.
   <p>The <dfn id=first-available-font>first available font</dfn>, used in the
    definition of <a
    href="http://www.w3.org/TR/css3-values/#font-relative-lengths"><em>font-relative
    lengths</em></a> such as ‘<code class=property>ex</code>’ and ‘<code
    class=property>ch</code>’, is defined to be the first available font
    that would match any character given font families in the ‘<code
    class=property>font-family</code>’ list (or a user agent's default font
    if none are available).
   <h3 id=cluster-matching><span class=secno>5.3 </span>Cluster matching</h3>
   <p>When text contains characters such as combining marks, ideally the base
    character should be rendered using the same font as the mark, this assures
    proper placement of the mark. For this reason, the font matching algorithm
    for clusters is more specialized than the general case of matching a
    single character by itself. For sequences containing variation selectors,
    which indicate the precise glyph to be used for a given character, user
    agents always attempt <a href="#system-font-fallback"><em>system font
    fallback</em></a> to find the appropriate glyph before using the default
    glyph of the base character.
   <p>A sequence of codepoints containing combining mark or other modifiers is
    termed a grapheme cluster (see <a href="#CSS3TEXT"
    rel=biblioentry>[CSS3TEXT]<!--{{CSS3TEXT}}--></a> for a more complete
    description). For a given cluster containing a base character, <em>b</em>
    and a sequence of combining characters <em>c1, c2…</em>, the entire
    cluster is matched using these steps:
   <ol>
    <li>For each family in the font list, a face is chosen using the style
     selection rules defined in the previous section.
     <ol>
      <li>If all characters in the sequence <em>b + c1 + c2 …</em> are
       completely supported by the font, select this font for the sequence.
      <li>If a sequence of multiple codepoints is canonically equivalent to a
       single character and the font <a href="#support"><em
       title=support>supports</em></a> that character, select this font for
       the sequence.
     </ol>
    <li>If no font was found in the font list in step 1:
     <ol>
      <li>If <em>c1</em> is a variation selector, system fallback must be used
       to find a font that <a href="#support"><em
       title=support>supports</em></a> the full sequence of <em>b + c1</em>.
       If no font on the system <a href="#support"><em
       title=support>supports</em></a> the full sequence, match the single
       character <em>b</em> using the normal procedure for matching single
       characters and ignore the variation selector. Note: a sequence with
       more than one variation selector must be treated as an encoding error
       and the trailing selectors must be ignored. <a href="#UNICODE6"
       rel=biblioentry>[UNICODE6]<!--{{!UNICODE6}}--></a>
      <li>Otherwise, the user agent may optionally use system font fallback to
       match a font that <a href="#support"><em
       title=support>supports</em></a> the entire cluster.
     </ol>
    <li>If no font is found in step 2, use the matching sequence from step 1
     to determine the longest sequence that is completely <a
     href="#support"><em title=support>supported</em></a> by a font in the
     font list and attempt to match the remaining combining characters
     separately using the rules for single characters.
   </ol>
   <h3 id=char-handling-issues><span class=secno>5.4 </span>Character handling
    issues</h3>
   <p>CSS font matching is always performed on text runs containing Unicode
    characters, so documents using legacy encodings are assumed to have been
    transcoded before matching fonts. For fonts containing <a
    href="#character-map"><em title="character map">character maps</em></a>
    for both legacy encodings and Unicode, the contents of the legacy encoding
    <a href="#character-map"><em>character map</em></a> must have no effect on
    the results of the font matching process.
   <p>The font matching process does not assume that text runs are in either
    normalized or denormalized form (see <a href="#CHARMOD-NORM"
    rel=biblioentry>[CHARMOD-NORM]<!--{{CHARMOD-NORM}}--></a> for more
    details). Fonts may only support precomposed forms and not the decomposed
    sequence of base character plus combining marks. Authors should always
    tailor their choice of fonts to their content, including whether that
    content contains normalized or denormalized character streams.
   <p>If a given character is a Private-Use Area Unicode codepoint, user
    agents must only match font families named in the ‘<code
    class=property>font-family</code>’ list that are not generic families.
    If none of the families named in the ‘<code
    class=property>font-family</code>’ list contain a glyph for that
    codepoint, user agents must display some form of missing glyph symbol for
    that character rather than attempting <a
    href="#system-font-fallback"><em>system font fallback</em></a> for that
    codepoint. When matching the replacement character U+FFFD, user agents may
    skip the font matching process and immediately display some form of
    missing glyph symbol, they are not required to display the glyph from the
    font that would be selected by the font matching process.
   <p>In general, the fonts for a given family will all have the same or
    similar <a href="#character-map"><em title="character map">character
    maps</em></a>. The process outlined here is designed to handle even font
    families containing faces with widely variant <a href="#character-map"><em
    title="character map">character maps</em></a>. However, authors are
    cautioned that the use of such families can lead to unexpected results.
   <h3 id=font-matching-changes><span class=secno>5.5 </span>Font matching
    changes since CSS 2.1</h3>
   <p>The algorithm above is different from CSS 2.1 in a number of key places.
    These changes were made to better reflect actual font matching behavior
    across user agent implementations.
   <p>Differences compared to the font matching algorithm in CSS 2.1:
   <ul>
    <li>The algorithm includes font-stretch matching.
    <li>All possible font-style matching scenarios are delineated.
    <li>Small-caps fonts are not matched as part of the font matching process,
     they are now handled via font features.
    <li>Unicode variation selector matching is required.
    <li>Cluster sequences are matched as a unit.
   </ul>
   <h3 id=font-matching-examples><span class=secno>5.6 </span>Font matching
    examples</h3>
   <div class=example>
    <p>It's useful to note that the CSS selector syntax may be used to create
     language-sensitive typography. For example, some Chinese and Japanese
     characters are unified to have the same Unicode code point, although the
     abstract glyphs are not the same in the two languages.
    <pre>*:lang(ja-jp) { font: 900 14pt/16pt &quot;Heisei Mincho W9&quot;, serif; }
 *:lang(zh-tw) { font: 800 14pt/16.5pt &quot;Li Sung&quot;, serif; }
 </pre>
    <p>This selects any element that has the given language — Japanese or
     Traditional Chinese — and uses the appropriate font.
   </div>
   <h2 id=font-rend-props><span class=secno>6 </span>Font Feature Properties</h2>
   <p>Modern font technologies support a variety of advanced typographic and
    language-specific font features. Using these features, a single font can
    provide glyphs for a wide range of ligatures, contextual and stylistic
    alternates, tabular and old-style figures, small capitals, automatic
    fractions, swashes, and alternates specific to a given language. To allow
    authors control over these font capabilities, the ‘<code
    class=property>font-variant</code>’ property has been expanded for CSS3.
    It now functions as a shorthand for a set of properties that provide
    control over stylistic font features.
   <h3 id=glyph-selection-positioning><span class=secno>6.1 </span>Glyph
    selection and positioning</h3>
   <p>Simple fonts used for displaying Latin text use a very basic processing
    model. Fonts contain a <a href="#character-map"><em>character map</em></a>
    which maps each character to a glyph for that character. Glyphs for
    subsequent characters are simply placed one after the other along a run of
    text. Modern font formats such as OpenType and AAT (Apple Advanced
    Typography) use a richer processing model. The glyph for a given character
    can be chosen and positioned not just based on the codepoint of the
    character itself, but also on adjacent characters as well as the language,
    script, and features enabled for the text. Font features may be required
    for specific scripts, or recommended as enabled by default or they might
    be stylistic features meant to be used under author control.
   <p>For a good visual overview of these features, see the <a
    href="#OPENTYPE-FONT-GUIDE"
    rel=biblioentry>[OPENTYPE-FONT-GUIDE]<!--{{OPENTYPE-FONT-GUIDE}}--></a>.
    For a detailed description of glyph processing for OpenType fonts, see <a
    href="#WINDOWS-GLYPH-PROC"
    rel=biblioentry>[WINDOWS-GLYPH-PROC]<!--{{WINDOWS-GLYPH-PROC}}--></a>.
   <p>Stylistic font features can be classified into two broad categories:
    ones that affect the harmonization of glyph shapes with the surrounding
    context, such as kerning and ligature features, and ones such as the
    small-caps, subscript/superscript and alternate features that affect shape
    selection.
   <p>The subproperties of <a href="#propdef-font-variant"
    title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> listed below are used to control
    these stylistic font features. They do not control features that are
    required for displaying certain scripts, such as the OpenType features
    used when displaying Arabic or Indic language text. They affect glyph
    selection and positioning, but do not affect font selection as described
    in the font matching section (except in cases required for compatibility
    with CSS 2.1).
   <p>To assure consistent behavior across user agents, the equivalent
    OpenType property settings are listed for individual properties and are
    normative. When using other font formats these should be used as a
    guideline to map CSS font feature property values to specific font
    features.
   <h3 id=language-specific-support><span class=secno>6.2
    </span>Language-specific display</h3>
   <p>OpenType also supports language-specific glyph selection and
    positioning, so that text can be displayed correctly in cases where the
    language dictates a specific display behavior. Many languages share a
    common script, but the shape of certain letters can vary across those
    languages. For example, certain Cyrillic letters have different shapes in
    Russian text than in Bulgarian. In Latin text, it's common to render "fi"
    with an explicit fi-ligature that lacks a dot on the "i". However, in
    languages such as Turkish which uses both a dotted-i and a dotless-i, it's
    important to not use this ligature or use a specialized version that
    contains a dot over the "i". The example below shows language-specific
    variations based on stylistic traditions found in Spanish, Italian and
    French orthography:
   <div class=featex><img alt="language specific forms, spanish"
    src=locl-1.png></div>
   <div class=featex><img alt="language specific forms, italian"
    src=locl-2.png></div>
   <div class=featex><img alt="language specific forms, french"
    src=locl-3.png></div>
   <p>If the content language of the element is known according to the rules
    of the <a
    href="http://www.w3.org/TR/CSS21/conform.html#doclanguage">document
    language</a>, user agents are required to infer the OpenType language
    system from the content language and use that when selecting and
    positioning glyphs using an OpenType font.
   <p>For OpenType fonts, in some cases it may be necessary to explicitly
    declare the OpenType language to be used, for example when displaying text
    in a given language that uses the typographic conventions of another
    language or when the font does not explicitly support a given language but
    supports a language that shares common typographic conventions. The ‘<a
    href="#propdef-font-language-override"><code
    class=property>font-language-override</code></a>’ property is used for
    this purpose.</p>
   <!-- prop: font-kerning -->
   <h3 id=font-kerning-prop><span class=secno>6.3 </span>Kerning: the <a
    href="#propdef-font-kerning">font-kerning</a> property</h3>
   <table class=propdef id=namefont-kerningvalueauto-normal-noneini>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-kerning>font-kerning</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-kerning-auto-value"
       title="auto!!font-kerning">auto</a> | <a
       href="#font-kerning-normal-value"
       title="normal!!font-kerning">normal</a> | <a
       href="#font-kerning-none-value" title="none!!font-kerning">none</a>
     <tr>
      <td>Initial:
      <td>auto
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>Kerning is the contextual adjustment of inter-glyph spacing. This
    property controls metric kerning, kerning that utilizes adjustment data
    contained in the font.
   <dl>
    <dt><dfn id=font-kerning-auto-value title="auto!!font-kerning">auto</dfn>
    <dd>Specifies that kerning is applied at the discretion of the user agent
    <dt><dfn id=font-kerning-normal-value
     title="normal!!font-kerning">normal</dfn>
    <dd>Specifies that kerning is applied
    <dt><dfn id=font-kerning-none-value title="none!!font-kerning">none</dfn>
    <dd>Specifies that kerning is not applied
   </dl>
   <p>For fonts that do not include kerning data this property will have no
    visible effect. When rendering with OpenType fonts, the <a
    href="#OPENTYPE" rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a>
    specification suggests that kerning be enabled by default. When kerning is
    enabled, the OpenType <span class=tag>kern</span> feature is enabled (for
    vertical text runs the <span class=tag>vkrn</span> feature is enabled
    instead). User agents must also support fonts that only support kerning
    via data contained in a <span class=tag>kern</span> font table, as
    detailed in the OpenType specification. If the ‘<code
    class=property>letter-spacing</code>’ property is defined, kerning
    adjustments are considered part of the default spacing and letter spacing
    adjustments are made after kerning has been applied.
   <p>When set to ‘<code class=property>auto</code>’, user agents can
    determine whether to apply kerning or not based on a number of factors:
    text size, script, or other factors that influence text processing speed.
    Authors who want proper kerning should use <a
    href="#font-kerning-normal-value" title="normal!!font-kerning">‘<code
    class=property>normal</code>’</a> to explicitly enable kerning.
    Likewise, some authors may prefer to disable kerning in situations where
    performance is more important than precise appearance. However, in
    well-designed modern implementations the use of kerning generally does not
    have a large impact on text rendering speed.</p>
   <!-- prop: font-variant-ligatures -->
   <h3 id=font-variant-ligatures-prop><span class=secno>6.4 </span>Ligatures:
    the <a href="#propdef-font-variant-ligatures">font-variant-ligatures</a>
    property</h3>
   <table class=propdef id=namefont-variant-ligaturesvaluenormal-no>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-variant-ligatures>font-variant-ligatures</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-variant-ligatures-normal-value"
       title="normal!!font-variant-ligatures">normal</a> | <a
       href="#font-variant-ligatures-none-value"
       title="none!!font-variant-ligatures">none</a> | [ <a
       href="#common-lig-values"><var>&lt;common-lig-values&gt;</var></a> ||
       <a
       href="#discretionary-lig-values"><var>&lt;discretionary-lig-values&gt;</var></a>
       || <a
       href="#historical-lig-values"><var>&lt;historical-lig-values&gt;</var></a>
       || <a
       href="#contextual-alt-values"><var>&lt;contextual-alt-values&gt;</var></a>
       ]
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>Ligatures and contextual forms are ways of combining glyphs to produce
    more harmonized forms.
   <pre
    class=prod><dfn id=common-lig-values><var>&lt;common-lig-values&gt;</var></dfn>        = [ <a href="#common-ligatures">common-ligatures</a> | <a href="#no-common-ligatures">no-common-ligatures</a> ]</pre>
   <pre
    class=prod><dfn id=discretionary-lig-values><var>&lt;discretionary-lig-values&gt;</var></dfn> = [ <a href="#discretionary-ligatures">discretionary-ligatures</a> | <a href="#no-discretionary-ligatures">no-discretionary-ligatures</a> ]</pre>
   <pre
    class=prod><dfn id=historical-lig-values><var>&lt;historical-lig-values&gt;</var></dfn>    = [ <a href="#historical-ligatures">historical-ligatures</a> | <a href="#no-historical-ligatures">no-historical-ligatures</a> ]</pre>
   <pre
    class=prod><dfn id=contextual-alt-values><var>&lt;contextual-alt-values&gt;</var></dfn>    = [ <a href="#contextual">contextual</a> | <a href="#no-contextual">no-contextual</a> ]</pre>
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=font-variant-ligatures-normal-value
     title="normal!!font-variant-ligatures">normal</dfn>
    <dd>A value of <a href="#font-variant-ligatures-normal-value"
     title="normal!!font-variant-ligatures">‘<code
     class=property>normal</code>’</a> specifies that common default
     features are enabled, <a href="#font-feature-resolution">as described in
     detail in the next section</a>. For OpenType fonts, common ligatures and
     contextual forms are on by default, discretionary and historical
     ligatures are not.
    <dt><dfn id=font-variant-ligatures-none-value
     title="none!!font-variant-ligatures">none</dfn>
    <dd>Specifies that all types of ligatures and contextual forms covered by
     this property are explicitly disabled. In situations where ligatures are
     not considered necessary, this may improve the speed of text rendering.
    <dt><dfn id=common-ligatures>common-ligatures</dfn>
    <dd>Enables display of common ligatures (OpenType features: <span
     class=tag>liga, clig</span>). For OpenType fonts, common ligatures are
     enabled by default.
   </dl>
   <div class=featex><img alt="common ligature example" src=liga.png></div>
   <dl>
    <dt><dfn id=no-common-ligatures>no-common-ligatures</dfn>
    <dd>Disables display of common ligatures (OpenType features: <span
     class=tag>liga, clig</span>).
    <dt><dfn id=discretionary-ligatures>discretionary-ligatures</dfn>
    <dd>Enables display of discretionary ligatures (OpenType feature: <span
     class=tag>dlig</span>). Which ligatures are discretionary or optional is
     decided by the type designer, so authors will need to refer to the
     documentation of a given font to understand which ligatures are
     considered discretionary.
   </dl>
   <div class=featex><img alt="discretionary ligature example" src=dlig.png></div>
   <dl>
    <dt><dfn id=no-discretionary-ligatures>no-discretionary-ligatures</dfn>
    <dd>Disables display of discretionary ligatures (OpenType feature: <span
     class=tag>dlig</span>).
    <dt><dfn id=historical-ligatures>historical-ligatures</dfn>
    <dd>Enables display of historical ligatures (OpenType feature: <span
     class=tag>hlig</span>).
   </dl>
   <div class=featex><img alt="historical ligature example" src=hlig.png></div>
   <dl>
    <dt><dfn id=no-historical-ligatures>no-historical-ligatures</dfn>
    <dd>Disables display of historical ligatures (OpenType feature: <span
     class=tag>hlig</span>).
    <dt><dfn id=contextual>contextual</dfn>
    <dd>Enables display of contextual alternates (OpenType feature: <span
     class=tag>calt</span>). Although not strictly a ligature feature, like
     ligatures this feature is commonly used to harmonize the shapes of glyphs
     with the surrounding context. For OpenType fonts, this feature is on by
     default.
   </dl>
   <div class=featex><img alt="contextual alternate example" src=calt.png></div>
   <dl>
    <dt><dfn id=no-contextual>no-contextual</dfn>
    <dd>Disables display of contextual alternates (OpenType feature: <span
     class=tag>calt</span>).
   </dl>
   <p>Required ligatures, needed for correctly rendering complex scripts, are
    not affected by the settings above, including ‘<code
    class=property>none</code>’ (OpenType feature: <span
    class=tag>rlig</span>).</p>
   <!-- prop: font-variant-position -->
   <h3 id=font-variant-position-prop><span class=secno>6.5 </span>Subscript
    and superscript forms: the <a
    href="#propdef-font-variant-position">font-variant-position</a> property</h3>
   <table class=propdef id=namefont-variant-positionvaluenormal-sub>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-variant-position>font-variant-position</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-variant-position-normal-value"
       title="normal!!font-variant-position">normal</a> | <a
       href="#sub">sub</a> | <a href="#super">super</a>
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>This property is used to enable typographic subscript and superscript
    glyphs. These are alternate glyphs designed within the same em-box as
    default glyphs and are intended to be laid out on the same baseline as the
    default glyphs, with no resizing or repositioning of the baseline. They
    are explicitly designed to match the surrounding text and to be more
    readable without affecting the line height.
   <div class=figure><img alt="comparison between real subscript glyphs and
    synthesized ones" src=realsubscripts.png>
    <p class=caption>Subscript glyphs (top) vs. typical synthesized subscripts
     (bottom)
   </div>
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=font-variant-position-normal-value
     title="normal!!font-variant-position">normal</dfn>
    <dd>None of the features listed below are enabled.
    <dt><dfn id=sub>sub</dfn>
    <dd>Enables display of subscript variants (OpenType feature: <span
     class=tag>subs</span>).
    <dt><dfn id=super>super</dfn>
    <dd>Enables display of superscript variants (OpenType feature: <span
     class=tag>sups</span>).
   </dl>
   <p>Because of the semantic nature of subscripts and superscripts, when the
    value is either ‘<a href="#sub"><code class=property>sub</code></a>’
    or ‘<a href="#super"><code class=property>super</code></a>’ for a
    given contiguous run of text, if a variant glyph is not available for all
    the characters in the run, simulated glyphs must be synthesized for all
    characters using reduced forms of the glyphs that would be used without
    this feature applied. This is done per run to avoid a mixture of variant
    glyphs and synthesized ones that would not align correctly. In the case of
    OpenType fonts that lack subscript or superscript glyphs for a given
    character, user agents must use the appropriate subscript and superscript
    metrics specified in the selected font's <a
    href="http://www.microsoft.com/typography/otspec/os2.htm#subxs">OS/2
    table</a> <a href="#OPENTYPE"
    rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a> to calculate the size
    and offset of the synthesized substitutes.
   <div class=figure><img alt="alternate superscripts vs. glyphs synthesized
    using superscript metrics" src=superscript-alt-synth.png>
    <p class=caption>Superscript alternate glyph (left), synthesized
     superscript glyphs (middle), and incorrect mixture of the two (right)
   </div>
   <p>In situations where text decorations are only applied to runs of text
    containing superscript or subscript glyphs, the synthesized glyphs must be
    used to avoid problems with the placement of decorations.
   <p>In the past, user agents have used font-size and vertical-align to
    simulate subscripts and superscripts for the <code title="HTML sub
    element">sub</code> and <code title="HTML sup element">sup</code>
    elements. To allow a backwards compatible way of defining subscripts and
    superscripts, it is recommended that authors use conditional rules <a
    href="#CSS3-CONDITIONAL"
    rel=biblioentry>[CSS3-CONDITIONAL]<!--{{CSS3-CONDITIONAL}}--></a> so that
    older user agents will still render subscripts and superscripts via the
    older mechanism.
   <p>Authors should note that fonts typically only provide subscript and
    superscript glyphs for a subset of all characters supported by the font.
    For example, while subscript and superscript glyphs are often available
    for Latin numbers, glyphs for punctuation and letter characters are less
    frequently provided. The synthetic fallback rules defined for this
    property assure that subscripts and superscripts will always appear but
    the appearance may not match author expectations if the font used does not
    provide the appropriate alternate glyph for all characters contained in a
    subscript or superscript.
   <p>This property is not cumulative. Applying it to elements within a
    subscript or superscript won't nest the placement of a subscript or
    superscript glyph. Images contained within text runs where the value of
    this property is ‘<a href="#sub"><code class=property>sub</code></a>’
    or ‘<a href="#super"><code class=property>super</code></a>’ will be
    drawn just as they would if the value was <a
    href="#font-variant-position-normal-value"
    title="normal!!font-variant-position">‘<code
    class=property>normal</code>’</a>.</p>
   <!-- due to lack of consensus, couldn't resolve on exact positioning of text decorations:
 http://www.w3.org/2013/06/06-css-minutes.html#item03 -->
   <p>Because of these limitations, ‘<a
    href="#propdef-font-variant-position"><code
    class=property>font-variant-position</code></a>’ is not recommended for
    use in user agent stylesheets. Authors should use it in cases where
    subscripts or superscripts will only contain the narrow range of
    characters supported by the fonts specified.
   <p class=note>The variant glyphs use the same baseline as the default
    glyphs would use. There is no shift in the placement along the baseline,
    so the use of variant glyphs doesn't affect the height of the inline box
    or alter the height of the linebox. This makes superscript and subscript
    variants ideal for situations where it's important that leading remain
    constant, such as in multi-column layout.
   <div class=example>
    <p>A typical user agent default style for the <a class=tag
     href="#sub">sub</a> element:</p>
    <pre>sub {
   vertical-align: sub;
   font-size: smaller;
   line-height: normal;
 }
 </pre>
    <p>Using font-variant-position to specify typographic subscripts in a way
     that will still show subscripts in older user agents:</p>
    <pre>@supports ( font-variant-position: sub ) {
   sub {
     vertical-align: baseline;
     font-size: 100%;
     line-height: inherit;
     font-variant-position: sub;
   }
 }
 </pre>
    <p>User agents that support the ‘<a
     href="#propdef-font-variant-position"><code
     class=property>font-variant-position</code></a>’ property will select a
     subscript variant glyph and render this without adjusting the baseline or
     font-size. Older user agents will ignore the ‘<a
     href="#propdef-font-variant-position"><code
     class=property>font-variant-position</code></a>’ property definition
     and use the standard defaults for subscripts.</p>
   </div>
   <!-- prop: font-variant-caps -->
   <h3 id=font-variant-caps-prop><span class=secno>6.6 </span>Capitalization:
    the <a href="#propdef-font-variant-caps">font-variant-caps</a> property</h3>
   <table class=propdef id=namefont-variant-capsvaluenormal-small-c>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-variant-caps>font-variant-caps</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-variant-caps-normal-value"
       title="normal!!font-variant-caps">normal</a> | <a
       href="#small-caps">small-caps</a> | <a
       href="#all-small-caps">all-small-caps</a> | <a
       href="#petite-caps">petite-caps</a> | <a
       href="#all-petite-caps">all-petite-caps</a> | <a
       href="#unicase">unicase</a> | <a href="#titling-caps">titling-caps</a>
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>This property allows the selection of alternate glyphs used for small or
    petite capitals or for titling. These glyphs are specifically designed to
    blend well with the surrounding normal glyphs, to maintain the weight and
    readability which suffers when text is simply resized to fit this purpose.
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=font-variant-caps-normal-value
     title="normal!!font-variant-caps">normal</dfn>
    <dd>None of the features listed below are enabled.
    <dt><dfn id=small-caps>small-caps</dfn>
    <dd>Enables display of small capitals (OpenType feature: <span
     class=tag>smcp</span>). Small-caps glyphs typically use the form of
     uppercase letters but are reduced to the size of lowercase letters.
   </dl>
   <div class=featex><img alt="small-caps example" src=smcp.png></div>
   <dl>
    <dt><dfn id=all-small-caps>all-small-caps</dfn>
    <dd>Enables display of small capitals for both upper and lowercase letters
     (OpenType features: <span class=tag>c2sc, smcp</span>).
    <dt><dfn id=petite-caps>petite-caps</dfn>
    <dd>Enables display of petite capitals (OpenType feature: <span
     class=tag>pcap</span>).
    <dt><dfn id=all-petite-caps>all-petite-caps</dfn>
    <dd>Enables display of petite capitals for both upper and lowercase
     letters (OpenType features: <span class=tag>c2pc, pcap</span>).
    <dt><dfn id=unicase>unicase</dfn>
    <dd>Enables display of mixture of small capitals for uppercase letters
     with normal lowercase letters (OpenType feature: <span
     class=tag>unic</span>).
    <dt><dfn id=titling-caps>titling-caps</dfn>
    <dd>Enables display of titling capitals (OpenType feature: <span
     class=tag>titl</span>). Uppercase letter glyphs are often designed for
     use with lowercase letters. When used in all uppercase titling sequences
     they can appear too strong. Titling capitals are designed specifically
     for this situation.
   </dl>
   <p>The availability of these glyphs is based on whether a given feature is
    defined or not in the feature list of the font. User agents can optionally
    decide this on a per-script basis but should explicitly not decide this on
    a per-character basis.
   <p>Some fonts may only support a subset or none of the features described
    for this property. For backwards compatibility with CSS 2.1, if ‘<a
    href="#small-caps"><code class=property>small-caps</code></a>’ or ‘<a
    href="#all-small-caps"><code class=property>all-small-caps</code></a>’
    is specified but small-caps glyphs are not available for a given font,
    user agents should simulate a small-caps font, for example by taking a
    normal font and replacing the glyphs for lowercase letters with scaled
    versions of the glyphs for uppercase characters (replacing the glyphs for
    both upper and lowercase letters in the case of ‘<a
    href="#all-small-caps"><code class=property>all-small-caps</code></a>’).
   <div class=figure style="padding: 0; margin: auto;"><img alt="synthetic vs.
    real small-caps" class=hires src=synthetic-vs-real-small-caps.png
    width=512>
    <p class=caption>Synthetic vs. real small-caps
   </div>
   <p>To match the surrounding text, a font may provide alternate glyphs for
    caseless characters when these features are enabled but when a user agent
    simulates small capitals, it must not attempt to simulate alternates for
    codepoints which are considered caseless.
   <div class=figure style="padding: 0; margin: auto;"><img alt="caseless
    characters with small-caps, all-small-caps enabled" class=hires
    src=small-capitals-variations.png width=418>
    <p class=caption>Caseless characters with small-caps, all-small-caps
     enabled
   </div>
   <p>If either ‘<a href="#petite-caps"><code
    class=property>petite-caps</code></a>’ or ‘<a
    href="#all-petite-caps"><code class=property>all-petite-caps</code></a>’
    is specified for a font that doesn't support these features, the property
    behaves as if ‘<a href="#small-caps"><code
    class=property>small-caps</code></a>’ or ‘<a
    href="#all-small-caps"><code class=property>all-small-caps</code></a>’,
    respectively, had been specified. If ‘<a href="#unicase"><code
    class=property>unicase</code></a>’ is specified for a font that doesn't
    support that feature, the property behaves as if ‘<a
    href="#small-caps"><code class=property>small-caps</code></a>’ was
    applied only to lowercased uppercase letters. If ‘<a
    href="#titling-caps"><code class=property>titling-caps</code></a>’ is
    specified with a font that does not support this feature, this property
    has no visible effect. When simulated small capital glyphs are used, for
    scripts that lack uppercase and lowercase letters, ‘<a
    href="#small-caps"><code class=property>small-caps</code></a>’, ‘<a
    href="#all-small-caps"><code class=property>all-small-caps</code></a>’,
    ‘<a href="#petite-caps"><code class=property>petite-caps</code></a>’,
    ‘<a href="#all-petite-caps"><code
    class=property>all-petite-caps</code></a>’ and ‘<a
    href="#unicase"><code class=property>unicase</code></a>’ have no visible
    effect.
   <p>When casing transforms are used to simulate small capitals, the casing
    transformations must match those used for the <span
    class=property>‘<code class=property>text-transform</code>’</span>
    property.
   <p>As a last resort, unscaled uppercase letter glyphs in a normal font may
    replace glyphs in a small-caps font so that the text appears in all
    uppercase letters.
   <div class=figure style="padding: 0; margin: auto;"><img alt="using
    all-small-caps in acronym-laden text" class=hires
    src=acronym-laden-text.png width=596>
    <p class=caption>Using small capitals to improve readability in
     acronym-laden text
   </div>
   <div class=example>
    <p>Quotes rendered italicised, with small-caps on the first line:</p>
    <pre>blockquote            { font-style: italic; }
 blockquote:first-line { font-variant: small-caps; }
 &lt;blockquote><a href="http://lists.w3.org/Archives/Public/www-style/2009Dec/0036.html" style="text-decoration: none; border: none;">I'll be honor-bound to slap them like a haddock.</a>&lt;/blockquote>
 </pre>
   </div>
   <!-- prop: font-variant-numeric -->
   <h3 id=font-variant-numeric-prop><span class=secno>6.7 </span>Numerical
    formatting: the <a
    href="#propdef-font-variant-numeric">font-variant-numeric</a> property</h3>
   <table class=propdef id=namefont-variant-numericvaluenormal-ltnu>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-variant-numeric>font-variant-numeric</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-variant-numeric-normal-value"
       title="normal!!font-variant-numeric">normal</a> | [ <a
       href="#numeric-figure-values"><var>&lt;numeric-figure-values&gt;</var></a>
       || <a
       href="#numeric-spacing-values"><var>&lt;numeric-spacing-values&gt;</var></a>
       || <a
       href="#numeric-fraction-values"><var>&lt;numeric-fraction-values&gt;</var></a>
       || <a href="#ordinal">ordinal</a> || <a
       href="#slashed-zero">slashed-zero</a> ]
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>Specifies control over numerical forms. The example below shows how some
    of these values can be combined to influence the rendering of tabular data
    with fonts that support these features. Within normal paragraph text,
    proportional numbers are used while tabular numbers are used so that
    columns of numbers line up properly:
   <div class=figure style="padding: 0; margin: auto;"><img alt="combining
    number styles" src=numberstyles.png>
    <p class=caption>Using number styles
   </div>
   <p>Possible combinations:
   <pre
    class=prod><dfn id=numeric-figure-values><var>&lt;numeric-figure-values&gt;</var></dfn>   = [ <a href="#lining-nums">lining-nums</a> | <a href="#oldstyle-nums">oldstyle-nums</a> ]</pre>
   <pre
    class=prod><dfn id=numeric-spacing-values><var>&lt;numeric-spacing-values&gt;</var></dfn>  = [ <a href="#proportional-nums">proportional-nums</a> | <a href="#tabular-nums">tabular-nums</a> ]</pre>
   <pre
    class=prod><dfn id=numeric-fraction-values><var>&lt;numeric-fraction-values&gt;</var></dfn> = [ <a href="#diagonal-fractions">diagonal-fractions</a> | <a href="#stacked-fractions">stacked-fractions</a> ]</pre>
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=font-variant-numeric-normal-value
     title="normal!!font-variant-numeric">normal</dfn>
    <dd>None of the features listed below are enabled.
    <dt><dfn id=lining-nums>lining-nums</dfn>
    <dd>Enables display of lining numerals (OpenType feature: <span
     class=tag>lnum</span>).
    <dt><dfn id=oldstyle-nums>oldstyle-nums</dfn>
    <dd>Enables display of old-style numerals (OpenType feature: <span
     class=tag>onum</span>).
    <dt><dfn id=proportional-nums>proportional-nums</dfn>
    <dd>Enables display of proportional numerals (OpenType feature: <span
     class=tag>pnum</span>).
    <dt><dfn id=tabular-nums>tabular-nums</dfn>
    <dd>Enables display of tabular numerals (OpenType feature: <span
     class=tag>tnum</span>).
    <dt><dfn id=diagonal-fractions>diagonal-fractions</dfn>
    <dd>Enables display of lining diagonal fractions (OpenType feature: <span
     class=tag>frac</span>).
   </dl>
   <div class=featex><img alt="diagonal fraction example" src=frac.png></div>
   <dl>
    <dt><dfn id=stacked-fractions>stacked-fractions</dfn>
    <dd>Enables display of lining stacked fractions (OpenType feature: <span
     class=tag>afrc</span>).
   </dl>
   <div class=featex><img alt="stacked fraction example" src=afrc.png></div>
   <dl>
    <dt><dfn id=ordinal>ordinal</dfn>
    <dd>Enables display of forms used with ordinal numbers (OpenType feature:
     <span class=tag>ordn</span>).
    <dt><dfn id=slashed-zero>slashed-zero</dfn>
    <dd>Enables display of slashed zeros (OpenType feature: <span
     class=tag>zero</span>).
   </dl>
   <div class=featex><img alt="slashed zero example" src=zero.png></div>
   <div class=example id=steak-marinade>
    <p>A simple flank steak marinade recipe, rendered with automatic fractions
     and old-style numerals:</p>
    <pre>.amount { font-variant-numeric: oldstyle-nums diagonal-fractions; }
 &lt;h4>Steak marinade:&lt;/h4>
 &lt;ul>
   &lt;li>&lt;span class="amount">2&lt;/span> tbsp olive oil&lt;/li>
   &lt;li>&lt;span class="amount">1&lt;/span> tbsp lemon juice&lt;/li>
   &lt;li>&lt;span class="amount">1&lt;/span> tbsp soy sauce&lt;/li>
   &lt;li>&lt;span class="amount">1 1/2&lt;/span> tbsp dry minced onion&lt;/li>
   &lt;li>&lt;span class="amount">2 1/2&lt;/span> tsp italian seasoning&lt;/li>
   &lt;li>Salt &amp;amp; pepper&lt;/li>
 &lt;/ul>
 &lt;p>Mix the meat with the marinade and let it sit covered in the refrigerator
 for a few hours or overnight.&lt;/p>
 </pre>
    <p>Note that the fraction feature is only applied to values not the entire
     paragraph. Fonts often implement this feature using contextual rules
     based on the use of the slash (‘<code class=css>/</code>’) character.
     As such, it's not suitable for use as a paragraph-level style.</p>
   </div>
   <!-- prop: font-variant-alternates -->
   <h3 id=font-variant-alternates-prop><span class=secno>6.8 </span>Alternates
    and swashes: the <a
    href="#propdef-font-variant-alternates">font-variant-alternates</a>
    property</h3>
   <table class=propdef id=namefont-variant-alternatesvaluenormal-s>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn
       id=propdef-font-variant-alternates>font-variant-alternates</dfn>
     <tr>
      <td>Value:
      <td>normal | [ <a href="#stylistic"
       title=stylistic>stylistic(&lt;feature-value-name&gt;)</a> || <a
       href="#historical-forms">historical-forms</a> || <a href="#styleset"
       title=styleset>styleset(&lt;feature-value-name&gt; #)</a> || <a
       href="#character-variant"
       title=character-variant>character-variant(&lt;feature-value-name&gt;
       #)</a> || <a href="#swash"
       title=swash>swash(&lt;feature-value-name&gt;)</a> || <a
       href="#ornaments"
       title=ornaments>ornaments(&lt;feature-value-name&gt;)</a> || <a
       href="#annotation"
       title=annotation>annotation(&lt;feature-value-name&gt;)</a> ]
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>For any given character, fonts can provide a variety of alternate glyphs
    in addition to the default glyph for that character. This property
    provides control over the selection of these alternate glyphs.
   <p>For many of the property values listed below, several different
    alternate glyphs are available. How many alternates are available and what
    they represent is font-specific, so these are each marked <dfn
    id=font-specific>font specific</dfn> in the value definitions below.
    Because the nature of these alternates is font-specific, the <a
    href="#at-font-feature-values-rule"><code>@font-feature-values</code></a>
    rule is used to define values for a specific font family or set of
    families that associate a font-specific numeric
    <code>&lt;feature-index&gt;</code> with a custom
    <code>&lt;feature-value-name&gt;</code>, which is then used in this
    property to select specific alternates:
   <pre>@font-feature-values Noble Script { @swash { swishy: 1; flowing: 2; } }
 p {
   font-family: Noble Script;
   font-variant-alternates: swash(flowing); /* use swash alternate #2 */
 }</pre>
   <p>When a particular <code>&lt;feature-value-name&gt;</code> has not been
    defined for a given family or for a particular feature type, the computed
    value must be the same as if it had been defined. However, property values
    that contain these undefined <code>&lt;feature-value-name&gt;</code>
    identifiers must be ignored when choosing glyphs.
   <pre>/* these two style rules are effectively the same */
 p { font-variant-alternates: swash(unknown-value); } /* not a defined value, ignored */
 p { font-variant-alternates: normal; }
 </pre>
   <p>This allows values to be defined and used for a given set of font
    families but ignored if fallback occurs, since the font family name would
    be different. If a given value is outside the range supported by a given
    font, the value is ignored. These values never apply to generic font
    families.
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=font-variant-alternates-normal-value
     title="normal!!font-variant-alternates">normal</dfn>
    <dd>None of the features listed below are enabled.
    <dt><dfn id=historical-forms>historical-forms</dfn>
    <dd>Enables display of historical forms (OpenType feature: <span
     class=tag>hist</span>).
   </dl>
   <div class=featex><img alt="historical form example" src=hist.png></div>
   <dl>
    <dt><dfn id=stylistic
     title=stylistic>stylistic(&lt;feature-value-name&gt;)</dfn>
    <dd>Enables display of stylistic alternates (<a
     href="#font-specific"><em>font specific</em></a>, OpenType feature: <span
     class=tag>salt &lt;feature-index&gt;</span>).
   </dl>
   <div class=featex><img alt="stylistic alternate example" src=salt.png></div>
   <dl>
    <dt><dfn id=styleset title=styleset>styleset(&lt;feature-value-name&gt;
     #)</dfn>
    <dd>Enables display with stylistic sets (<a href="#font-specific"><em>font
     specific</em></a>, OpenType feature: <span
     class=tag>ss&lt;feature-index&gt;</span> OpenType currently defines <span
     class=tag>ss01</span> through <span class=tag>ss20</span>).
   </dl>
   <div class=featex><img alt="styleset example" src=ssnn.png></div>
   <dl>
    <dt><dfn id=character-variant
     title=character-variant>character-variant(&lt;feature-value-name&gt;
     #)</dfn>
    <dd>Enables display of specific character variants (<a
     href="#font-specific"><em>font specific</em></a>, OpenType feature: <span
     class=tag>cv&lt;feature-index&gt;</span> OpenType currently defines <span
     class=tag>cv01</span> through <span class=tag>cv99</span>).
    <dt><dfn id=swash title=swash>swash(&lt;feature-value-name&gt;)</dfn>
    <dd>Enables display of swash glyphs (<a href="#font-specific"><em>font
     specific</em></a>, OpenType feature: <span class=tag>swsh
     &lt;feature-index&gt;, cswh &lt;feature-index&gt;</span>).
   </dl>
   <div class=featex><img alt="swash example" src=swsh.png></div>
   <dl>
    <dt><dfn id=ornaments
     title=ornaments>ornaments(&lt;feature-value-name&gt;)</dfn>
    <dd>Enables replacement of default glyphs with ornaments, if provided in
     the font (<a href="#font-specific"><em>font specific</em></a>, OpenType
     feature: <span class=tag>ornm &lt;feature-index&gt;</span>). Some fonts
     may offer ornament glyphs as alternates for a wide collection of
     characters; however, displaying arbitrary characters (e.g.,
     alphanumerics) as ornaments is poor practice as it distorts the semantics
     of the data. Font designers are encouraged to encode all ornaments
     (except those explicitly encoded in the Unicode Dingbats blocks, etc.) as
     alternates for the bullet character (U+2022) to allow authors to select
     the desired glyph using ‘<a href="#ornaments"><code
     class=property>ornaments</code></a>’.
   </dl>
   <div class=featex><img alt="ornaments example" src=ornm.png></div>
   <dl>
    <dt><dfn id=annotation
     title=annotation>annotation(&lt;feature-value-name&gt;)</dfn>
    <dd>Enables display of alternate annotation forms (<a
     href="#font-specific"><em>font specific</em></a>, OpenType feature: <span
     class=tag>nalt &lt;feature-index&gt;</span>).
   </dl>
   <div class=featex><img alt="alternate annotation form example"
    src=nalt.png></div>
   <h3 id=font-feature-values><span class=secno>6.9 </span>Defining font
    specific alternates: the <dfn id=at-font-feature-values-rule
    style="font-weight: inherit; font-style:
    inherit"><code>@font-feature-values</code></dfn> rule</h3>
   <p>Several of the possible values of ‘<a
    href="#propdef-font-variant-alternates"><code
    class=property>font-variant-alternates</code></a>’ listed above are
    labeled as <a href="#font-specific"><em>font specific</em></a>. For these
    features fonts may define not just a single glyph but a set of alternate
    glyphs with an index to select a given alternate. Since these are font
    family specific, the <a
    href="#at-font-feature-values-rule"><code>@font-feature-values</code></a>
    rule is used to define named values for these indices for a given family.
   <p class=note>See the <a href="#om-fontfeaturevalues">object model
    reference section</a> for a description of the interfaces used to modify
    these rules via the CSS Object Model.
   <div class=example>
    <p>In the case of the swash Q in the example shown above, the swash could
     be specified using these style rules:</p>
    <pre>
 @font-feature-values Jupiter Sans {
   @swash {
     delicate: 1;
     flowing: 2;
   }
 }
 h2 { font-family: Jupiter Sans, sans-serif; }
 /* show the second swash variant in h2 headings */
 h2:first-letter { font-variant-alternates: swash(flowing); }
 &lt;h2>Quick&lt;/h2></pre>
    <p>When Jupiter Sans is present, the second alternate swash alternate will
     be displayed. When not present, no swash character will be shown, since
     the specific named value "flowing" is only defined for the Jupiter Sans
     family. The @-mark indicates the name of the property value for which a
     named value can be used. The name "flowing" is chosen by the author. The
     index that represents each alternate is defined within a given font's
     data.</p>
   </div>
   <h4 id=basic-syntax><span class=secno>6.9.1 </span>Basic syntax</h4>
   <p>An <a
    href="#at-font-feature-values-rule"><code>@font-feature-values</code></a>
    rule is composed of a list of font families followed by a block containing
    individual <a href="#featurevalueblock"><i
    title="feature_value_block">feature value blocks</i></a> that take the
    form of @-rules. Each block defines a set of named values for a specific
    font feature when a given set of font families is used. Effectively, they
    define a mapping of ⟨family, feature, ident⟩ → ⟨values⟩ where
    ⟨values⟩ are the numeric indices used for specific features defined
    for a given font.
   <p>In terms of the grammar, this specification defines the following
    productions:
   <pre><dfn id=fontfeaturevaluesrule>font_feature_values_rule</dfn>
   : <a href="#fontfeaturevaluessym"><i>FONT_FEATURE_VALUES_SYM</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#fontfamilynamelist"><i>font_family_name_list</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
     '{' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#featurevalueblock"><i>feature_value_block</i></a>? [ <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#featurevalueblock"><i>feature_value_block</i></a>? ]* '}' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
   ;
 <dfn id=fontfamilynamelist>font_family_name_list</dfn>
   : <a href="#fontfamilyname"><i>font_family_name</i></a> [ <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* ',' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#fontfamilyname"><i>font_family_name</i></a> ]*
   ;
 <dfn id=fontfamilyname>font_family_name</dfn>
   : <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>STRING</i></a> | [ <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>IDENT</i></a> [ <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>IDENT</i></a> ]* ]
   ;
 <dfn id=featurevalueblock>feature_value_block</dfn>
   : <a href="#featuretype"><i>feature_type</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
     '{' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#featurevaluedefinition"><i>feature_value_definition</i></a>? [ <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* ';' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#featurevaluedefinition"><i>feature_value_definition</i></a>? ]* '}' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
   ;
 <dfn id=featuretype>feature_type</dfn>:
   <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>ATKEYWORD</i></a>
   ;
 <dfn id=featurevaluedefinition>feature_value_definition</dfn>
   : <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>IDENT</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* ':' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>NUMBER</i></a> [ <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>NUMBER</i></a> ]*
   ;
 </pre>
   <p>The following new token is introduced:
   <pre>@{F}{O}{N}{T}{-}{F}{E}{A}{T}{U}{R}{E}{-}{V}{A}{L}{U}{E}{S}   {return <dfn id=fontfeaturevaluessym>FONT_FEATURE_VALUES_SYM</dfn>;}
 </pre>
   <p><a href="#featurevalueblock"><i title="feature_value_block">Feature
    value blocks</i></a> are handled as <a
    href="http://www.w3.org/TR/CSS2/syndata.html#at-rules">at-rules</a>, they
    consist of everything up to the next block or semi-colon, whichever comes
    first.
   <p>The <a href="#fontfamilynamelist"><i title="font_family_name_list">font
    family list</i></a> is a comma-delimited list of <a
    href="#fontfamilyname"><i title="font_family_name">font family
    names</i></a> that match the definition of <a
    href="#family-name-value"><var>&lt;family-name&gt;</var></a> for the <a
    href="#propdef-font-family" title="font-family!!property">‘<code
    class=property>font-family</code>’</a> property. This means that only
    named font families are allowed, rules that include generic or system
    fonts in the list of font families are syntax errors. However, if a user
    agent defines a generic font to be a specific named font (e.g. Helvetica),
    the settings associated with that family name will be used. If syntax
    errors occur within the font family list, the entire rule must be ignored.
   <p>Within <a href="#featurevalueblock"><i
    title="feature_value_block">feature value blocks</i></a>, the <a
    href="#featuretype"><i title="feature_type">feature type</i></a> is
    ‘<code class=css>@</code>’ followed by the name of one of the <a
    href="#font-specific"><em>font specific</em></a> property values of ‘<a
    href="#propdef-font-variant-alternates"><code
    class=property>font-variant-alternates</code></a>’ (e.g. <a
    href="#swash"><code>@swash</code></a>). The identifiers used within
    feature value definitions follow the rules of CSS user identifiers and are
    case-sensitive. They are unique only for a given set of font families and
    <a href="#featuretype"><i title="feature_type">feature type</i></a>. The
    same identifier used with a different <a href="#featuretype"><i
    title="feature_type">feature type</i></a> is treated as a separate and
    distinct value. If the same identifier is defined mulitple times for a
    given <a href="#featuretype"><i title="feature_type">feature type</i></a>
    and font family, the last defined value is used. Values associated with a
    given identifier are limited to integer values 0 or greater.
   <p>When syntax errors occur within a <a href="#featurevaluedefinition"><i
    title="feature_value_definition">feature value definition</i></a>, such as
    invalid identifiers or values, the entire <a
    href="#featurevaluedefinition"><i title="feature_value_definition">feature
    value definition</i></a> must be omitted, just as syntax errors in style
    declarations are handled. When the <a href="#featuretype"><i
    title="feature_type">feature type</i></a> is invalid, the entire
    associated <a href="#featurevalueblock"><i
    title="feature_value_block">feature value block</i></a> must be ignored.
   <div class=example>
    <p>Rules that are equivalent given syntax error handling:</p>
    <pre>@font-feature-values Bongo {
   @swash { ornate: 1; }
   annotation { boxed: 4; } /* should be @annotation! */
   @swash { double-loops: 1; flowing: -1; } /* negative value */
   @ornaments ; /* incomplete definition */
   @styleset { double-W: 14; sharp-terminals: 16 1 } /* missing ; */
   <a href="http://www.angryalien.com/0504/shiningbunnies.html" style="text-decoration: none; border: none;">redrum</a>  /* random editing mistake */
 }</pre>
    <p>The example above is equivalent to:</p>
    <pre>@font-feature-values Bongo {
   @swash { ornate: 1; }
   @swash { double-loops: 1; }
   @styleset { double-W: 14; sharp-terminals: 16 1; }
 }</pre>
   </div>
   <p>If multiple <a
    href="#at-font-feature-values-rule"><code>@font-feature-values</code></a>
    rules are defined for a given family, the resulting values definitions are
    the union of the definitions contained within these rules. This allows a
    set of named values to be defined for a given font family globally for a
    site and specific additions made per-page.
   <div class=example>
    <p>Using both site-wide and per-page feature values:</p>
    <pre>
 site.css:
   @font-feature-values Mercury Serif {
     @styleset {
       stacked-g: 3; /* "two-storey" versions of g, a */
       stacked-a: 4;
     }
   }
 page.css:
   @font-feature-values Mercury Serif {
     @styleset {
       geometric-m: 7; /* alternate version of m */
     }
   }
   body {
     font-family: Mercury Serif, serif;
     /* enable both the use of stacked g and alternate m */
     font-variant-alternates: styleset(stacked-g, geometric-m);
   }</pre>
   </div>
   <div class=example>
    <p>Using a commonly named value allows authors to use a single style rule
     to cover a set of fonts for which the underlying selector is different
     for each font. If either font in the example below is found, a circled
     number glyph will be used:</p>
    <pre>@font-feature-values Taisho Gothic {
   @annotation { boxed: 1; circled: 4; }
 }
 @font-feature-values Otaru Kisa {
   @annotation { circled: 1; black-boxed: 3; }
 }
 h3.title {
   /* circled form defined for both fonts */
   font-family: Taisho Gothic, Otaru Kisa;
   font-variant: annotation(circled);
 }</pre>
   </div>
   <h4 id=multi-valued-feature-value-definitions><span class=secno>6.9.2
    </span>Multi-valued feature value definitions</h4>
   <p>Most <a href="#font-specific"><em>font specific</em></a> ‘<a
    href="#propdef-font-variant-alternates"><code
    class=property>font-variant-alternates</code></a>’ property values take
    a single value (e.g. ‘<a href="#swash"><code
    class=property>swash</code></a>’). The ‘<a
    href="#character-variant"><code
    class=property>character-variant</code></a>’ property value allows two
    values and ‘<a href="#styleset"><code
    class=property>styleset</code></a>’ allows an unlimited number.
   <p>For the styleset property value, multiple values indicate the style sets
    to be enabled. Values between 1 and 99 enable OpenType features <span
    class=tag>ss01</span> through <span class=tag>ss99</span>. However, the
    OpenType standard only officially defines <span class=tag>ss01</span>
    through <span class=tag>ss20</span>. For OpenType fonts, values greater
    than 99 or equal to 0 do not generate a syntax error when parsed but
    enable no OpenType features.
   <pre>@font-feature-values Mars Serif {
   @styleset {
     alt-g: 1;        /* implies ss01 = 1 */
     curly-quotes: 3; /* implies ss03 = 1 */
     code: 4 5;       /* implies ss04 = 1, ss05 = 1 */
   }
   @styleset {
     dumb: 125;        /* &gt;99, ignored */
   }
   @swash {
     swishy: 3 5;     /* more than 1 value for swash, syntax error */
   }
 }
 p.codeblock {
   /* implies ss03 = 1, ss04 = 1, ss05 = 1 */
   font-variant-alternates: styleset(curly-quotes, code);
 }</pre>
   <p>For character-variant, a single value between 1 and 99 indicates the
    enabling of OpenType feature <span class=tag>cv01</span> through <span
    class=tag>cv99</span>. For OpenType fonts, values greater than 99 or equal
    to 0 are ignored but do not generate a syntax error when parsed but enable
    no OpenType features. When two values are listed, the first value
    indicates the feature used and the second the value passed for that
    feature. If more than two values are assigned to a given name, a syntax
    error occurs and the entire <a href="#featurevaluedefinition"><i
    title="feature_value_definition">feature value definition</i></a> is
    ignored.
   <pre>@font-feature-values MM Greek {
   @character-variant { alpha-2: 1 2; }   /* implies cv01 = 2 */
   @character-variant { beta-3: 2 3; }    /* implies cv02 = 3 */
   @character-variant { epsilon: 5 3 6; } /* more than 2 values, syntax error, definition ignored */
   @character-variant { gamma: 12; }      /* implies cv12 = 1 */
   @character-variant { zeta:   20 3; }   /* implies cv20 = 3 */
   @character-variant { zeta-2: 20 2; }   /* implies cv20 = 2 */
   @character-variant { silly: 105; }     /* &gt;99, ignored */
   @character-variant { dumb: 323 3; }    /* &gt;99, ignored */
 }
 #title {
   /* use the third alternate beta, first alternate gamma */
   font-variant-alternates: character-variant(beta-3, gamma);
 }
 p {
   /* zeta-2 follows zeta, implies cv20 = 2  */
   font-variant-alternates: character-variant(zeta, zeta-2);
 }
 .special {
   /* zeta follows zeta-2, implies cv20 = 3  */
   font-variant-alternates: character-variant(zeta-2, zeta);
 }</pre>
   <div class=figure><img alt="Matching text on Byzantine seals using
    character variants" src=byzantineseal.png>
    <p class=caption>Byzantine seal text displayed with character variants
   </div>
   <div class=example>
    <p>In the figure above, the text in red is rendered using a font
     containing character variants that mimic the character forms found on a
     Byzantine seal from the 8th century A.D. Two lines below is the same text
     displayed in a font without variants. Note the two variants for U and N
     used on the seal.</p>
    <pre>@font-feature-values Athena Ruby {
   @character-variant {
     leo-B: 2 1;
     leo-M: 13 3;
     leo-alt-N: 14 1;
     leo-N: 14 2;
     leo-T: 20 1;
     leo-U: 21 2;
     leo-alt-U: 21 4;
   }
 }
 p {
   font-variant: discretionary-ligatures,
                 character-variant(leo-B, leo-M, leo-N, leo-T, leo-U);
 }
 span.alt-N {
   font-variant-alternates: character-variant(leo-alt-N);
 }
 span.alt-U {
   font-variant-alternates: character-variant(leo-alt-U);
 }
 &lt;p>ENO....UP͞RSTU&lt;span class="alt-U">U&lt;/span>͞&lt;span class="alt-U">U&lt;/span>ΚΑΙTỤẠG̣IUPNS&lt;/p>
 &lt;p>LEON|ΚΑΙCONSTA|NTI&lt;span class="alt-N">N&lt;/span>OS..|STOIBAṢ.|LIṢROM|AIO&lt;span class="alt-N">N&lt;/span>&lt;/p>
 </pre>
   </div>
   <h3 id=font-variant-east-asian-prop><span class=secno>6.10 </span>East
    Asian text rendering: the <a
    href="#propdef-font-variant-east-asian">font-variant-east-asian</a>
    property</h3>
   <table class=propdef id=namefont-variant-east-asianvaluenormal-l>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn
       id=propdef-font-variant-east-asian>font-variant-east-asian</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-variant-east-asian-normal-value"
       title="normal!!font-variant-east-asian">normal</a> | [ <a
       href="#east-asian-variant-values"><var>&lt;east-asian-variant-values&gt;</var></a>
       || <a
       href="#east-asian-width-values"><var>&lt;east-asian-width-values&gt;</var></a>
       || <a href="#ruby">ruby</a> ]
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>Allows control of glyph substitution and sizing in East Asian text.
   <pre
    class=prod><dfn id=east-asian-variant-values><var>&lt;east-asian-variant-values&gt;</var></dfn> = [ <a href="#jis78">jis78</a> | <a href="#jis83">jis83</a> | <a href="#jis90">jis90</a> | <a href="#jis04">jis04</a> | <a href="#simplified">simplified</a> | <a href="#traditional">traditional</a> ]</pre>
   <pre
    class=prod><dfn id=east-asian-width-values><var>&lt;east-asian-width-values&gt;</var></dfn>   = [ <a href="#full-width">full-width</a> | <a href="#proportional-width">proportional-width</a> ]</pre>
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=font-variant-east-asian-normal-value
     title="normal!!font-variant-east-asian">normal</dfn>
    <dd>None of the features listed below are enabled.
    <dt><dfn id=jis78>jis78</dfn>
    <dd>Enables rendering of JIS78 forms (OpenType feature: <span
     class=tag>jp78</span>).
   </dl>
   <div class=featex><img alt="JIS78 form example" src=jp78.png></div>
   <dl>
    <dt><dfn id=jis83>jis83</dfn>
    <dd>Enables rendering of JIS83 forms (OpenType feature: <span
     class=tag>jp83</span>).
    <dt><dfn id=jis90>jis90</dfn>
    <dd>Enables rendering of JIS90 forms (OpenType feature: <span
     class=tag>jp90</span>).
    <dt><dfn id=jis04>jis04</dfn>
    <dd>Enables rendering of JIS2004 forms (OpenType feature: <span
     class=tag>jp04</span>).
     <p>The various JIS variants reflect the glyph forms defined in different
      Japanese national standards. Fonts generally include glyphs defined by
      the most recent national standard but it's sometimes necessary to use
      older variants, to match signage for example.</p>
    <dt><dfn id=simplified>simplified</dfn>
    <dd>Enables rendering of simplified forms (OpenType feature: <span
     class=tag>smpl</span>).
    <dt><dfn id=traditional>traditional</dfn>
    <dd>Enables rendering of traditional forms (OpenType feature: <span
     class=tag>trad</span>).
   </dl>
   <p>The ‘<a href="#simplified"><code
    class=property>simplified</code></a>’ and ‘<a
    href="#traditional"><code class=property>traditional</code></a>’ values
    allow control over the glyph forms for characters which have been
    simplified over time but for which the older, traditional form is still
    used in some contexts. The exact set of characters and glyph forms will
    vary to some degree by context for which a given font was designed.
   <div class=featex><img alt="tradtional form example" src=trad.png></div>
   <dl>
    <dt><dfn id=full-width>full-width</dfn>
    <dd>Enables rendering of full-width variants (OpenType feature: <span
     class=tag>fwid</span>).
    <dt><dfn id=proportional-width>proportional-width</dfn>
    <dd>Enables rendering of proportionally-spaced variants (OpenType feature:
     <span class=tag>pwid</span>).
   </dl>
   <div class=featex><img alt="proportionally spaced Japanese example"
    src=pwid.png></div>
   <dl>
    <dt><dfn id=ruby>ruby</dfn>
    <dd>Enables display of ruby variant glyphs (OpenType feature: <span
     class=tag>ruby</span>). Since ruby text is generally smaller than the
     associated body text, font designers can design special glyphs for use
     with ruby that are more readable than scaled down versions of the default
     glyphs. Only glyph selection is affected, there is no associated font
     scaling or other change that affects line layout. The red ruby text below
     is shown with default glyphs (top) and with ruby variant glyphs (bottom).
     Note the slight difference in stroke thickness.
   </dl>
   <div class=featex><img alt="ruby variant example" src=rubyshinkansen.png></div>
   <h3 id=font-variant-prop><span class=secno>6.11 </span>Overall shorthand
    for font rendering: the <a href="#propdef-font-variant">font-variant</a>
    property</h3>
   <table class=propdef id=namefont-variantvaluenormal-none-ltcommo>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-variant
       title="font-variant!!property">font-variant</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-variant-normal-value"
       title="normal!!font-variant">normal</a> | <a
       href="#font-variant-none-value" title="none!!font-variant">none</a> | [
       <a href="#common-lig-values"><var>&lt;common-lig-values&gt;</var></a>
       || <a
       href="#discretionary-lig-values"><var>&lt;discretionary-lig-values&gt;</var></a>
       || <a
       href="#historical-lig-values"><var>&lt;historical-lig-values&gt;</var></a>
       || <a
       href="#contextual-alt-values"><var>&lt;contextual-alt-values&gt;</var></a>
       || <a href="#stylistic"><var
       title=stylistic>stylistic(&lt;feature-value-name&gt;)</var></a> || <a
       href="#historical-forms"><var>historical-forms</var></a> || <a
       href="#styleset"><var
       title=styleset>styleset(&lt;feature-value-name&gt; #)</var></a> || <a
       href="#character-variant"><var
       title=character-variant>character-variant(&lt;feature-value-name&gt;
       #)</var></a> || <a href="#swash"><var
       title=swash>swash(&lt;feature-value-name&gt;)</var></a> || <a
       href="#ornaments"><var
       title=ornaments>ornaments(&lt;feature-value-name&gt;)</var></a> || <a
       href="#annotation"><var
       title=annotation>annotation(&lt;feature-value-name&gt;)</var></a> || [
       <a href="#small-caps"><i>small-caps</i></a> | <a
       href="#all-small-caps"><i>all-small-caps</i></a> | <a
       href="#petite-caps"><i>petite-caps</i></a> | <a
       href="#all-petite-caps"><i>all-petite-caps</i></a> | <a
       href="#unicase"><i>unicase</i></a> | <a
       href="#titling-caps"><i>titling-caps</i></a> ] || <a
       href="#numeric-figure-values"><var>&lt;numeric-figure-values&gt;</var></a>
       || <a
       href="#numeric-spacing-values"><var>&lt;numeric-spacing-values&gt;</var></a>
       || <a
       href="#numeric-fraction-values"><var>&lt;numeric-fraction-values&gt;</var></a>
       || <a href="#ordinal"><i>ordinal</i></a> || <a
       href="#slashed-zero"><i>slashed-zero</i></a> || <a
       href="#east-asian-variant-values"><var>&lt;east-asian-variant-values&gt;</var></a>
       || <a
       href="#east-asian-width-values"><var>&lt;east-asian-width-values&gt;</var></a>
       || <a href="#ruby"><i>ruby</i></a> ]
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>see individual properties
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>see individual properties
     <tr>
      <td>Animatable:
      <td>see individual properties
   </table>
   <p>The <a href="#propdef-font-variant"
    title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> property is a shorthand for all
    font-variant subproperties. The value <dfn id=font-variant-normal-value
    title="normal!!font-variant">‘<code
    class=property>normal</code>’</dfn> resets all subproperties of <a
    href="#propdef-font-variant" title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> to their inital value. The <dfn
    id=font-variant-none-value title="none!!font-variant">‘<code
    class=property>none</code>’</dfn> value sets ‘<a
    href="#propdef-font-variant-ligatures"><code
    class=property>font-variant-ligatures</code></a>’ to ‘<code
    class=property>none</code>’ and resets all other font feature properties
    to their initial value. Like other shorthands, using <a
    href="#propdef-font-variant" title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> resets unspecified <a
    href="#propdef-font-variant" title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> subproperties to their initial
    values. It does not reset the values of either ‘<a
    href="#propdef-font-language-override"><code
    class=property>font-language-override</code></a>’ or <a
    href="#propdef-font-feature-settings"
    title="font-feature-settings!!property">‘<code
    class=property>font-feature-settings</code>’</a>.
   <h3 id=font-feature-settings-prop><span class=secno>6.12 </span>Low-level
    font feature settings control: the <a
    href="#propdef-font-feature-settings">font-feature-settings</a> property</h3>
   <table class=propdef id=namefont-feature-settingsvaluenormal-ltf>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-feature-settings
       title="font-feature-settings!!property">font-feature-settings</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-feature-settings-normal-value"
       title="normal!!font-feature-settings">normal</a> | <a
       href="#feature-tag-value"><var>&lt;feature-tag-value&gt;</var></a> #
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>This property provides low-level control over OpenType font features. It
    is intended as a way of providing access to font features that are not
    widely used but are needed for a particular use case.
   <p>Authors should generally use <a href="#propdef-font-variant"
    title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> and its related subproperties
    whenever possible and only use this property for special cases where its
    use is the only way of accessing a particular infrequently used font
    feature.
   <pre>/* enable small caps and use second swash alternate */
 font-feature-settings: "smcp", "swsh" 2;</pre>
   <p>A value of <dfn id=font-feature-settings-normal-value
    title="normal!!font-feature-settings">‘<code
    class=property>normal</code>’</dfn> means that no change in glyph
    selection or positioning occurs due to this property.
   <p>Feature tag values have the following syntax:
   <pre
    class=prod><dfn id=feature-tag-value><var>&lt;feature-tag-value&gt;</var></dfn> = &lt;string&gt; [ &lt;integer&gt; | on | off ]?</pre>
   <p>The &lt;string&gt; is a case-sensitive OpenType feature tag. As
    specified in the OpenType specification, feature tags contain four ASCII
    characters. Tag strings longer or shorter than four characters, or
    containing characters outside the U+20–7E codepoint range are invalid.
    Feature tags need only match a feature tag defined in the font, so they
    are not limited to explicitly registered OpenType features. Fonts defining
    custom feature tags should follow the <a
    href="http://www.microsoft.com/typography/otspec/featuretags.htm">tag name
    rules</a> defined in the OpenType specification <a
    href="#OPENTYPE-FEATURES"
    rel=biblioentry>[OPENTYPE-FEATURES]<!--{{!OPENTYPE-FEATURES}}--></a>.
   <p>Feature tags not present in the font are ignored; a user agent must not
    attempt to synthesize fallback behavior based on these feature tags. The
    one exception is that user agents may synthetically support the <span
    class=tag>kern</span> feature with fonts that contain kerning data in the
    form of a ‘<code class=property>kern</code>’ table but lack <span
    class=tag>kern</span> feature support in the ‘<code
    class=property>GPOS</code>’ table.
   <p class=note>In general, authors should use the ‘<a
    href="#propdef-font-kerning"><code
    class=property>font-kerning</code></a>’ property to explicitly enable or
    disable kerning since this property always affects fonts with either type
    of kerning data.
   <p>If present, a value indicates an index used for glyph selection. An
    &lt;integer&gt; value must be 0 or greater. A value of 0 indicates that
    the feature is disabled. For boolean features, a value of 1 enables the
    feature. For non-boolean features, a value of 1 or greater enables the
    feature and indicates the feature selection index. A value of ‘<code
    class=property>on</code>’ is synonymous with 1 and ‘<code
    class=property>off</code>’ is synonymous with 0. If the value is
    omitted, a value of 1 is assumed.
   <pre>
 font-feature-settings: "dlig" 1;       /* dlig=1 enable discretionary ligatures */
 font-feature-settings: "smcp" on;      /* smcp=1 enable small caps */
 font-feature-settings: 'c2sc';         /* c2sc=1 enable caps to small caps */
 font-feature-settings: "liga" off;     /* liga=0 no common ligatures */
 font-feature-settings: "tnum", 'hist'; /* tnum=1, hist=1 enable tabular numbers and historical forms */
 font-feature-settings: "tnum" "hist";  /* invalid, need a comma-delimited list */
 font-feature-settings: "silly" off;    /* invalid, tag too long */
 font-feature-settings: "PKRN";         /* PKRN=1 enable custom feature */
 font-feature-settings: dlig;           /* invalid, tag must be a string */
 </pre>
   <p>When values greater than the range supported by the font are specified,
    the behavior is explicitly undefined. For boolean features, in general
    these will enable the feature. For non-boolean features, out of range
    values will in general be equivalent to a 0 value. However, in both cases
    the exact behavior will depend upon the way the font is designed
    (specifically, which type of lookup is used to define the feature).
   <p>Although specifically defined for OpenType feature tags, feature tags
    for other modern font formats that support font features may be added in
    the future. Where possible, features defined for other font formats should
    attempt to follow the pattern of registered OpenType tags.
   <div class=example>
    <p>The Japanese text below will be rendered with half-width kana
     characters:</p>
    <pre lang=ja>
 body { font-feature-settings: "hwid"; /* Half-width OpenType feature */ }
 &lt;p>毎日<a href="http://images.google.com/images?q=%E3%82%AB%E3%83%AC%E3%83%BC" style="text-decoration: none;">カレー</a>食べてるのに、飽きない&lt;/p>
 </pre>
   </div>
   <h3 id=font-language-override-prop><span class=secno>6.13 </span>Font
    language override: the <a
    href="#propdef-font-language-override">font-language-override</a> property</h3>
   <table class=propdef id=namefont-language-overridevaluenormal-lt>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-language-override>font-language-override</dfn>
     <tr>
      <td>Value:
      <td><a href="#font-language-override-normal-value"
       title="normal!!font-language-override">normal</a> | <a
       href="#font-language-override-string-value"><var>&lt;string&gt;</var></a>
     <tr>
      <td>Initial:
      <td><a href="#font-language-override-normal-value"
       title="normal!!font-language-override">normal</a>
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>Normally, authors can control the use of language-specific glyph
    substitutions and positioning by setting the content language of an
    element, as <a href="#language-specific-support">described above</a>:
   <pre>&lt;!-- Display text using S'gaw Karen specific features -->
 &lt;p lang="ksw">...&lt;/p></pre>
   <p>In some cases, authors may need to specify a language system that
    differs from the content language, for example due to the need to mimic
    another language's typographic traditions. The ‘<a
    href="#propdef-font-language-override"><code
    class=property>font-language-override</code></a>’ property allows
    authors to explicitly specify the language system of the font, overriding
    the language system implied by the content language.
   <p>Values have the following meanings:
   <dl>
    <dt><dfn id=font-language-override-normal-value
     title="normal!!font-language-override">normal</dfn>
    <dd>specifies that when rendering with OpenType fonts, the content
     language of the element is used to infer the OpenType language system
    <dt><dfn
     id=font-language-override-string-value><var>&lt;string&gt;</var></dfn>
    <dd>single three-letter case-sensitive OpenType <a
     href="http://www.microsoft.com/typography/otspec/languagetags.htm">language
     system tag</a>, specifies the OpenType language system to be used instead
     of the language system implied by the language of the element
   </dl>
   <!-- For this level, string represents a single language code, there's no concept of "fallback"
 http://www.w3.org/2013/06/07-css-minutes.html#item04 -->
   <p>Use of invalid OpenType language system tags must not generate a parse
    error but must be ignored when doing glyph selection and placement.
   <div class=example>
    <p>The <a href="http://www.un.org/en/documents/udhr/index.shtml">Universal
     Declaration of Human Rights</a> has been translated into a wide variety
     of languages. In Turkish, Article 9 of this document might be marked up
     as below:</p>
    <pre lang=tr>&lt;body lang="tr">
 &lt;h4>Madde 9&lt;/h4>
 &lt;p>Hiç kimse keyfi olarak tutuklanamaz, alıkonulanamaz veya sürülemez.&lt;/p>
 </pre>
    <p>Here the user agent uses the value of the ‘<code
     class=property>lang</code>’ attribute when rendering text and
     appropriately renders this text without ‘<code
     class=property>fi</code>’ ligatures. There is no need to use the ‘<a
     href="#propdef-font-language-override"><code
     class=property>font-language-override</code></a>’ property.</p>
    <p>However, a given font may lack support for a specific language. In this
     situation authors may need to use the typographic conventions of a
     related language that are supported by that font:</p>
    <pre lang=mk>&lt;body lang="mk">     &lt;!-- Macedonian lang code --&gt;
 body { font-language-override: "SRB"; /* Serbian OpenType language tag */ }
 &lt;h4>Члeн 9&lt;/h4>
 &lt;p>Никoj чoвeк нeмa дa бидe пoдлoжeн нa прoизвoлнo aпсeњe, притвoр или прoгoнувaњe.&lt;/p>
 </pre>
    <p>The Macedonian text here will be rendered using Serbian typographic
     conventions, with the assumption that the font specified supports
     Serbian.</p>
   </div>
   <p><a id=rendering-considerations></a>
   <h2 id=font-feature-resolution><span class=secno>7 </span>Font Feature
    Resolution</h2>
   <p>As described in the previous section, font features can be enabled in a
    variety of ways, either via the use of <a href="#propdef-font-variant"
    title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> or <a
    href="#propdef-font-feature-settings"
    title="font-feature-settings!!property">‘<code
    class=property>font-feature-settings</code>’</a> in a style rule or
    within an <a href="#at-font-face-rule"><code>@font-face</code></a> rule.
    The resolution order for the union of these settings is defined below.
    Features defined via CSS properties are applied on top of layout engine
    default features.
   <h3 id=default-features><span class=secno>7.1 </span>Default features</h3>
   <p>For OpenType fonts, user agents must enable the default features defined
    in the OpenType documentation for a given script and writing mode.
    Required ligatures, common ligatures and contextual forms must be enabled
    by default (OpenType features: <span class=tag>rlig, liga, clig,
    calt</span>), along with localized forms (OpenType feature: <span
    class=tag>locl</span>), and features required for proper display of
    composed characters and marks (OpenType features: <span class=tag>ccmp,
    mark, mkmk</span>). These features must always be enabled, even when the
    value of the <a href="#propdef-font-variant"
    title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> and <a
    href="#propdef-font-feature-settings"
    title="font-feature-settings!!property">‘<code
    class=property>font-feature-settings</code>’</a> properties is <span
    title="normal value">‘<code class=property>normal</code>’</span>.
    Individual features are only disabled when explicitly overridden by the
    author, as when ‘<a href="#propdef-font-variant-ligatures"><code
    class=property>font-variant-ligatures</code></a>’ is set to ‘<a
    href="#no-common-ligatures"><code
    class=property>no-common-ligatures</code></a>’. For handling complex
    scripts such as <a
    href="http://www.microsoft.com/typography/otfntdev/arabicot/features.aspx">Arabic</a>,
    <a
    href="http://www.microsoft.com/typography/otfntdev/mongolot/features.htm">Mongolian</a>
    or <a
    href="http://www.microsoft.com/typography/otfntdev/devanot/features.aspx">Devanagari</a>
    additional features are required. For upright text within vertical text
    runs, vertical alternates (OpenType feature: <span class=tag>vert</span>)
    must be enabled.
   <h3 id=feature-precedence><span class=secno>7.2 </span>Feature precedence</h3>
   <p>General and <a href="#font-specific"><em>font specific</em></a> font
    feature property settings are resolved in the order below, in ascending
    order of precedence. This ordering is used to construct a combined list of
    font features that affect a given text run.
   <ol>
    <li>Font features enabled by default, including features required for a
     given script.
    <li>If the font is defined via an <a
     href="#at-font-face-rule"><code>@font-face</code></a> rule, the font
     features implied by the font-variant descriptor in the <a
     href="#at-font-face-rule"><code>@font-face</code></a> rule.
    <li>If the font is defined via an <a
     href="#at-font-face-rule"><code>@font-face</code></a> rule, the font
     features implied by the font-feature-settings descriptor in the <a
     href="#at-font-face-rule"><code>@font-face</code></a> rule.
    <li>Font features implied by the value of the <a
     href="#propdef-font-variant" title="font-variant!!property">‘<code
     class=property>font-variant</code>’</a> property, the related <a
     href="#propdef-font-variant" title="font-variant!!property">‘<code
     class=property>font-variant</code>’</a> subproperties and any other CSS
     property that uses OpenType features (e.g. the ‘<a
     href="#propdef-font-kerning"><code
     class=property>font-kerning</code></a>’ property).</li>
    <!-- other CSS props override 'font-variant' but not 'font-feature-settings' -->
    <!-- http://lists.w3.org/Archives/Public/www-style/2013Aug/0110.html -->
    <li>Feature settings determined by properties other than <a
     href="#propdef-font-variant" title="font-variant!!property">‘<code
     class=property>font-variant</code>’</a> or <a
     href="#propdef-font-feature-settings"
     title="font-feature-settings!!property">‘<code
     class=property>font-feature-settings</code>’</a>. For example, setting
     a non-default value for the ‘<code
     class=property>letter-spacing</code>’ property disables common
     ligatures.
    <li>Font features implied by the value of <a
     href="#propdef-font-feature-settings"
     title="font-feature-settings!!property">‘<code
     class=property>font-feature-settings</code>’</a> property.
   </ol>
   <p>This ordering allows authors to set up a general set of defaults for
    fonts within their <a
    href="#at-font-face-rule"><code>@font-face</code></a> rules, then override
    them with property settings for specific elements. General property
    settings override the settings in <a
    href="#at-font-face-rule"><code>@font-face</code></a> rules and low-level
    font feature settings override <a href="#propdef-font-variant"
    title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> property settings.
   <p>For situations where the combined list of font feature settings contains
    more than one value for the same feature, the last value is used. When a
    font lacks support for a given underlying font feature, text is simply
    rendered as if that font feature was not enabled; font fallback does not
    occur and no attempt is made to synthesize the feature except where
    explicitly defined for specific properties.
   <h3 id=feature-precedence-examples><span class=secno>7.3 </span>Feature
    precedence examples</h3>
   <div class=example>
    <p>With the styles below, numbers are rendered proportionally when used
     within a paragraph but are shown in tabular form within tables of prices:</p>
    <pre>body {
   font-variant-numeric: proportional-nums;
 }
 table.prices td {
   font-variant-numeric: tabular-nums;
 }
 </pre>
   </div>
   <div class=example>
    <p>When the <a href="#descdef-font-variant"
     title="font-variant!!descriptor">font-variant</a> descriptor is used
     within an <a href="#at-font-face-rule"><code>@font-face</code></a> rule,
     it only applies to the font defined by that rule.</p>
    <pre>@font-face {
   font-family: MainText;
   src: url(http://example.com/font.woff);
   font-variant: oldstyle-nums proportional-nums styleset(1,3);
 }
 body {
   font-family: MainText, Helvetica;
 }
 table.prices td {
   font-variant-numeric: tabular-nums;
 }
 </pre>
    <p>In this case, old-style numerals will be used throughout but only where
     the font "MainText" is used. Just as in the previous example, tabular
     values will be used in price tables since ‘<a
     href="#tabular-nums"><code class=property>tabular-nums</code></a>’
     appears in a general style rule and its use is mutually exclusive with
     ‘<a href="#proportional-nums"><code
     class=property>proportional-nums</code></a>’. Stylistic alternate sets
     will only be used where MainText is used.</p>
   </div>
   <div class=example>
    <p>The <a href="#at-font-face-rule"><code>@font-face</code></a> rule can
     also be used to access font features in locally available fonts via the
     use of <code>local()</code> in the ‘<a href="#descdef-src"><code
     class=property>src</code></a>’ descriptor of the <a
     href="#at-font-face-rule"><code>@font-face</code></a> definition:</p>
    <pre>@font-face {
   font-family: BodyText;
   src: local("HiraMaruPro-W4");
   font-variant: proportional-width;
   font-feature-settings: "ital"; /* Latin italics within CJK text feature */
 }
 body { font-family: BodyText, serif; }
 </pre>
    <p>If available, a Japanese font "Hiragino Maru Gothic" will be used. When
     text rendering occurs, Japanese kana will be proportionally spaced and
     Latin text will be italicised. Text rendered with the fallback serif font
     will use default rendering properties.</p>
   </div>
   <div class=example>
    <p>In the example below, discretionary ligatures are enabled only for a
     downloadable font but are disabled within spans of class "special":</p>
    <pre>@font-face {
   font-family: main;
   src: url(fonts/ffmeta.woff) format("woff");
   font-variant: discretionary-ligatures;
 }
 body         { font-family: main, Helvetica; }
 span.special { font-variant-ligatures: no-discretionary-ligatures; }
 </pre>
    <p>Suppose one adds a rule using ‘<code
     class=property>font-feature-settings</code>’ to enable discretionary
     ligatures:</p>
    <pre>body         { font-family: main, Helvetica; }
 span         { font-feature-settings: "dlig"; }
 span.special { font-variant-ligatures: no-discretionary-ligatures; }
 </pre>
    <p>In this case, discretionary ligatures <em>will</em> be rendered within
     spans of class "special". This is because both the <a
     href="#propdef-font-feature-settings"
     title="font-feature-settings!!property">‘<code
     class=property>font-feature-settings</code>’</a> and ‘<a
     href="#propdef-font-variant-ligatures"><code
     class=property>font-variant-ligatures</code></a>’ properties apply to
     these spans. Although the ‘<code class=css>no-discretionary
     ligatures</code>’ setting of ‘<a
     href="#propdef-font-variant-ligatures"><code
     class=property>font-variant-ligatures</code></a>’ effectively disables
     the OpenType <span class=tag>dlig</span> feature, because the <a
     href="#propdef-font-feature-settings"
     title="font-feature-settings!!property">‘<code
     class=property>font-feature-settings</code>’</a> is resolved after
     that, the ‘<code class=property>dlig</code>’ value reenables
     discretionary ligatures.</p>
   </div>
   <h2 id=object-model><span class=secno>8 </span>Object Model</h2>
   <p>The contents of <a href="#at-font-face-rule"><code>@font-face</code></a>
    and <a
    href="#at-font-feature-values-rule"><code>@font-feature-values</code></a>
    rules can be accessed via the following extensions to the CSS Object
    Model.
   <h3 id=om-fontface><span class=secno>8.1 </span>The <a
    href="#cssfontfacerule"><code>CSSFontFaceRule</code></a> interface</h3>
   <p>The <dfn id=cssfontfacerule>CSSFontFaceRule</dfn> interface represents a
    <a href="#at-font-face-rule"><code>@font-face</code></a> rule.
   <pre class=idl>
 interface CSSFontFaceRule : CSSRule {
   attribute DOMString family;
   attribute DOMString src;
   attribute DOMString style;
   attribute DOMString weight;
   attribute DOMString stretch;
   attribute DOMString unicodeRange;
   attribute DOMString variant;
   attribute DOMString featureSettings;
 }</pre>
   <p>The DOM Level 2 Style specification <a href="#DOM-LEVEL-2-STYLE"
    rel=biblioentry>[DOM-LEVEL-2-STYLE]<!--{{DOM-LEVEL-2-STYLE}}--></a>
    defined a different variant of this rule. This definition supercedes that
    one.
   <h3 id=om-fontfeaturevalues><span class=secno>8.2 </span>The <a
    href="#cssfontfeaturevaluesrule"><code>CSSFontFeatureValuesRule</code></a>
    interface</h3>
   <p>The <code>CSSRule</code> interface is extended as follows:
   <pre class=idl>partial interface CSSRule {
   const unsigned short FONT_FEATURE_VALUES_RULE = 14;
 }</pre>
   <p>The <dfn id=cssfontfeaturevaluesrule>CSSFontFeatureValuesRule</dfn>
    interface represents a <a
    href="#at-font-feature-values-rule"><code>@font-feature-values</code></a>
    rule.
   <pre class=idl>interface CSSFontFeatureValuesRule : CSSRule {
   attribute DOMString fontFamily;
   readonly attribute CSSFontFeatureValuesMap annotation;
   readonly attribute CSSFontFeatureValuesMap ornaments;
   readonly attribute CSSFontFeatureValuesMap stylistic;
   readonly attribute CSSFontFeatureValuesMap swash;
   readonly attribute CSSFontFeatureValuesMap characterVariant;
   readonly attribute CSSFontFeatureValuesMap styleset;
 }
 [MapClass(DOMString, sequence&lt;unsigned long&gt;)]
 interface CSSFontFeatureValuesMap {
   void set(DOMString featureValueName,
            (unsigned long or sequence&lt;unsigned long&gt;) values);
 }</pre>
   <dl class=idl-attributes>
    <dt><var>fontFamily</var> of type <code>DOMString</code>
    <dd>The list of one or more font families for which a given set of feature
     values is defined.
    <dt>value maps of type <code>CSSFontFeatureValuesMap</code>, readonly
    <dd>Maps of feature values associated with feature value names for a given
     ‘<a href="#propdef-font-variant-alternates"><code
     class=property>font-variant-alternates</code></a>’ value type
   </dl>
   <p>Each value map attribute of <a
    href="#cssfontfeaturevaluesrule"><code>CSSFontFeatureValuesRule</code></a>
    reflects the values defined via a corresponding <a
    href="#featurevalueblock"><i title="feature_value_block">feature value
    block</i></a>. Thus, the <var title="annotation
    attribute">annotation</var> attribute contains the values contained within
    a <code title="@annotation">@annotation</code> <a
    href="#featurevalueblock"><i title="feature_value_block">feature value
    block</i></a>, the <var title="ornaments attribute">ornaments</var>
    attribute contains the values contained with a <code
    title="@ornaments">@ornaments</code> <a href="#featurevalueblock"><i
    title="feature_value_block">feature value block</i></a> and so forth.
   <p>The <code>CSSFontFeatureValuesMap</code> interface uses the <a
    href="http://dev.w3.org/2006/webapi/WebIDL/#es-map-members">default map
    class methods</a> but the <code>set</code> method has different behavior.
    It takes a sequence of unsigned integers and associates it with a given
    <code>featureValueName</code>. The method behaves the same as the default
    map class method except that a single unsigned long value is treated as a
    sequence of a single value. The method throws an exception if an invalid
    number of values is passed in. If the associated <a
    href="#featurevalueblock"><i title="feature_value_block">feature value
    block</i></a> only allows a limited number of values, the <code>set</code>
    method throws an <code>InvalidAccessError</code> exception when the input
    sequence to <code>set</code> contains more than the limited number of
    values. See the description of <a
    href="#multi-valued-feature-value-definitions">multi-valued feature value
    definitions</a> for details on the maximum number of values allowed for a
    given type of <a href="#featurevalueblock"><i
    title="feature_value_block">feature value block</i></a>. The
    <code>get</code> method always returns a sequence of values, even if the
    sequence only contains a single value.
   <h2 class=no-num id=platform-props-to-css>Appendix A: Mapping platform font
    properties to CSS properties</h2>
   <p><em>This appendix is included as background for some of the problems and
    situations that are described in other sections. It should be viewed as
    informative only.</em>
   <p>Font properties in CSS are designed to be independent of the underlying
    font formats used; they can be used to specify bitmap fonts, Type1 fonts,
    SVG fonts in addition to the common TrueType and OpenType fonts. But there
    are facets of the TrueType and OpenType formats that often cause confusion
    for authors and present challenges to implementers on different platforms.
   <p>Originally developed at Apple, TrueType was designed as an outline font
    format for both screen and print. Microsoft joined Apple in developing the
    TrueType format and both platforms have supported TrueType fonts since
    then. Font data in the TrueType format consists of a set of tables
    distinguished with common four-letter tag names, each containing a
    specific type of data. For example, naming information, including
    copyright and license information, is stored in the ‘<code
    class=property>name</code>’ table. The <a
    href="#character-map"><em>character map</em></a> (‘<code
    class=property>cmap</code>’) table contains a mapping of character
    encodings to glyphs. Apple later added additional tables for supporting
    enhanced typographic functionality; these are now called Apple Advanced
    Typography, or AAT, fonts. Microsoft and Adobe developed a separate set of
    tables for advanced typography and called their format OpenType <a
    href="#OPENTYPE" rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a>.
   <p>In many cases the font data used under Microsoft Windows or Linux is
    slightly different from the data used under Apple's Mac OS X because the
    TrueType format allowed for explicit variation across platforms. This
    includes font metrics, names and <a href="#character-map"><em>character
    map</em></a> data.
   <p>Specifically, font family name data is handled differently across
    platforms. For TrueType and OpenType fonts these names are contained in
    the ‘<code class=property>name</code>’ table, in name records with
    name ID 1. Mulitple names can be stored for different locales, but
    Microsoft recommends fonts always include at least a US English version of
    the name. On Windows, Microsoft made the decision for backwards
    compatibility to limit this family name to a maximum of four faces; for
    larger groupings the "preferred family" (name ID 16) or "WWS family" (name
    ID 21) can be used. Other platforms such as OSX don't have this
    limitation, so the family name is used to define all possible groupings.
   <p>Other name table data provides names used to uniquely identify a
    specific face within a family. The full font name (name ID 4) and the
    Postscript name (name ID 6) describe a single face uniquely. For example,
    the bold face of the Gill Sans family has a fullname of "Gill Sans Bold"
    and a Postscript name of "GillSans-Bold". There can be multiple localized
    versions of the fullname for a given face, but the Postscript name is
    always a unique name made from a limited set of ASCII characters.
   <p>On various platforms, different names are used to search for a font. For
    example, with the Windows GDI CreateIndirectFont API, either a family or
    fullname can be used to lookup a face, while on Mac OS X the
    CTFontCreateWithName API call is used to lookup a given face using the
    fullname and Postscript name. Under Linux, the fontconfig API allows fonts
    to be searched using any of these names. In situations where platform
    API's automatically substitute other font choices, it may be necessary to
    verify a returned font matches a given name.
   <p>The weight of a given face can be determined via the usWeightClass field
    of the OS/2 table or inferred from the style name (name ID 2). Likewise,
    the width can be determined via the usWidthClass of the OS/2 table or
    inferred from the style name. For historical reasons related to synthetic
    bolding at weights 200 or lower with the Windows GDI API, font designers
    have sometimes skewed values in the OS/2 table to avoid these weights.
   <p>Rendering complex scripts that use contextual shaping such as Thai,
    Arabic and Devanagari requires features present only in OpenType or AAT
    fonts. Currently, complex script rendering is supported on Windows and
    Linux using OpenType font features while both OpenType and AAT font
    features are used under Mac OS X.
   <h2 class=no-num id=ch-ch-ch-changes>Changes</h2>
   <h3 class=no-num id=recent-changes> Changes from the <a
    href="http://www.w3.org/TR/2013/WD-css-fonts-3-20130711/">July 2013 CSS3
    Fonts Last Call Working Draft</a></h3>
   <p>Major changes include:
   <ul>
    <li>reorder feature precedence such that features implied by other CSS
     properties override ‘<code class=property>font-variant</code>’
     settings
    <li>switched examples to use .woff files
    <li>revised wording of font fetching algorithm
    <li>clarify meaning of <a href="#font-size-adjust-auto-value"
     title="auto!!font-size-adjust">‘<code class=property>auto</code>’</a>
     value for ‘<a href="#propdef-font-size-adjust"><code
     class=property>font-size-adjust</code></a>’
    <li>allow user agents to synthesize OpenType <span class=tag>kern</span>
     feature
    <li>minor editorial cleanups
   </ul>
   <h2 class=no-num id=acknowledgments>Acknowledgments</h2>
   <p>I'd like to thank Tal Leming, Jonathan Kew and Christopher Slye for all
    their help and feedback. John Hudson was kind enough to take the time to
    explain the subtleties of OpenType language tags and provided the example
    of character variant usage for displaying text on Byzantine seals. Ken
    Lunde and Eric Muller provided valuable feedback on CJK OpenType features
    and Unicode variation selectors. The idea for supporting font features by
    using <a href="#propdef-font-variant"
    title="font-variant!!property">‘<code
    class=property>font-variant</code>’</a> subproperties originated with
    Håkon Wium Lie, Adam Twardoch and Tal Leming. Elika Etemad supplied some
    of the initial design ideas for the <a
    href="#at-font-feature-values-rule"><code>@font-feature-values</code></a>
    rule. Thanks also to House Industries for allowing the use of Ed Interlock
    in the discretionary ligatures example.
   <p>A special thanks to Robert Bringhurst for the sublime mind expansion
    that is <em>The Elements of Typographic Style</em>.
   <h2 class=no-num id=conformance> Conformance</h2>
   <h3 class=no-num id=conventions> Document Conventions</h3>
   <p>Conformance requirements are expressed with a combination of descriptive
    assertions and RFC 2119 terminology. The key words “MUST”, “MUST
    NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”,
    “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the
    normative parts of this document are to be interpreted as described in RFC
 . However, for readability, these words do not appear in all uppercase
    letters in this specification.
   <p>All of the text of this specification is normative except sections
    explicitly marked as non-normative, examples, and notes. <a
    href="#RFC2119" rel=biblioentry>[RFC2119]<!--{{!RFC2119}}--></a>
   <p>Examples in this specification are introduced with the words “for
    example” or are set apart from the normative text with
    <code>class="example"</code>, like this:
   <div class=example>
    <p>This is an example of an informative example.
   </div>
   <p>Informative notes begin with the word “Note” and are set apart from
    the normative text with <code>class="note"</code>, like this:
   <p class=note>Note, this is an informative note.
   <h3 class=no-num id=conformance-classes> Conformance Classes</h3>
   <p>Conformance to CSS Fonts Level 3 Module is defined for three conformance
    classes:
   <dl>
    <dt><dfn id=style-sheet title="style sheet!!as conformance class">style
     sheet</dfn>
    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
     style sheet</a>.
    <dt><dfn id=renderer>renderer</dfn>
    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
     that interprets the semantics of a style sheet and renders documents that
     use them.
    <dt><dfn id=authoring-tool>authoring tool</dfn>
    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
     that writes a style sheet.
   </dl>
   <p>A style sheet is conformant to CSS Fonts Level 3 Module if all of its
    declarations that use properties defined in this module have values that
    are valid according to the generic CSS grammar and the individual grammars
    of each property as given in this module.
   <p>A renderer is conformant to CSS Fonts Level 3 Module if, in addition to
    interpreting the style sheet as defined by the appropriate specifications,
    it supports all the features defined by CSS Fonts Level 3 Module by
    parsing them correctly and rendering the document accordingly. However,
    the inability of a UA to correctly render a document due to limitations of
    the device does not make the UA non-conformant. (For example, a UA is not
    required to render color on a monochrome monitor.)
   <p>An authoring tool is conformant to CSS Fonts Level 3 Module if it writes
    style sheets that are syntactically correct according to the generic CSS
    grammar and the individual grammars of each feature in this module, and
    meet all other conformance requirements of style sheets as described in
    this module.
   <h3 class=no-num id=partial> Partial Implementations</h3>
   <p>So that authors can exploit the forward-compatible parsing rules to
    assign fallback values, CSS renderers <strong>must</strong> treat as
    invalid (and <a
    href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore as
    appropriate</a>) any at-rules, properties, property values, keywords, and
    other syntactic constructs for which they have no usable level of support.
    In particular, user agents <strong>must not</strong> selectively ignore
    unsupported component values and honor supported values in a single
    multi-value property declaration: if any value is considered invalid (as
    unsupported values must be), CSS requires that the entire declaration be
    ignored.
   <h3 class=no-num id=experimental> Experimental Implementations</h3>
   <p>To avoid clashes with future CSS features, the CSS2.1 specification
    reserves a <a
    href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
    syntax</a> for proprietary and experimental extensions to CSS.
   <p>Prior to a specification reaching the Candidate Recommendation stage in
    the W3C process, all implementations of a CSS feature are considered
    experimental. The CSS Working Group recommends that implementations use a
    vendor-prefixed syntax for such features, including those in W3C Working
    Drafts. This avoids incompatibilities with future changes in the draft.
   <h3 class=no-num id=testing> Non-Experimental Implementations</h3>
   <p>Once a specification reaches the Candidate Recommendation stage,
    non-experimental implementations are possible, and implementors should
    release an unprefixed implementation of any CR-level feature they can
    demonstrate to be correctly implemented according to spec.
   <p>To establish and maintain the interoperability of CSS across
    implementations, the CSS Working Group requests that non-experimental CSS
    renderers submit an implementation report (and, if necessary, the
    testcases used for that implementation report) to the W3C before releasing
    an unprefixed implementation of any CSS features. Testcases submitted to
    W3C are subject to review and correction by the CSS Working Group.
   <p>Further information on submitting testcases and implementation reports
    can be found from on the CSS Working Group's website at <a
    href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
    Questions should be directed to the <a
    href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a>
    mailing list.
   <h2 class=no-num id=references>References</h2>
   <h3 class=no-num id=normative-references>Normative References</h3>
   <!--begin-normative-->
   <!-- Sorted by label -->
   <dl class=bibliography>
    <dd style="display: none"><!-- keeps the doc valid if the DL is empty -->
     <!---->
    <dt id=CHARMOD>[CHARMOD]
    <dd>Martin J. Dürst; et al. <a
     href="http://www.w3.org/TR/2005/REC-charmod-20050215/"><cite>Character
     Model for the World Wide Web 1.0: Fundamentals.</cite></a> 15 February
 . W3C Recommendation. URL: <a
     href="http://www.w3.org/TR/2005/REC-charmod-20050215/">http://www.w3.org/TR/2005/REC-charmod-20050215/</a>
     </dd>
    <!---->
    <dt id=CORS>[CORS]
    <dd>Anne van Kesteren. <a
     href="http://www.w3.org/TR/2013/CR-cors-20130129/"><cite>Cross-Origin
     Resource Sharing.</cite></a> 29 January 2013. W3C Candidate
     Recommendation. (Work in progress.) URL: <a
     href="http://www.w3.org/TR/2013/CR-cors-20130129/">http://www.w3.org/TR/2013/CR-cors-20130129/</a>
     </dd>
    <!---->
    <dt id=CSS21>[CSS21]
    <dd>Bert Bos; et al. <a
     href="http://www.w3.org/TR/2011/REC-CSS2-20110607"><cite>Cascading Style
     Sheets Level 2 Revision 1 (CSS 2.1) Specification.</cite></a> 7 June
 . W3C Recommendation. URL: <a
     href="http://www.w3.org/TR/2011/REC-CSS2-20110607">http://www.w3.org/TR/2011/REC-CSS2-20110607</a>
     </dd>
    <!---->
    <dt id=CSS3VAL>[CSS3VAL]
    <dd>Håkon Wium Lie; Tab Atkins; Elika J. Etemad. <a
     href="http://www.w3.org/TR/2013/CR-css3-values-20130404/"><cite>CSS
     Values and Units Module Level 3.</cite></a> 4 April 2013. W3C Candidate
     Recommendation. (Work in progress.) URL: <a
     href="http://www.w3.org/TR/2013/CR-css3-values-20130404/">http://www.w3.org/TR/2013/CR-css3-values-20130404/</a>
     </dd>
    <!---->
    <dt id=HTML5>[HTML5]
    <dd>Ian Hickson. <a
     href="http://www.w3.org/TR/2012/CR-html5-20121217/"><cite>HTML5.</cite></a>
 December 2012. W3C Candidate Recommendation. (Work in progress.) URL:
     <a
     href="http://www.w3.org/TR/2012/CR-html5-20121217/">http://www.w3.org/TR/2012/CR-html5-20121217/</a>
     </dd>
    <!---->
    <dt id=OPEN-FONT-FORMAT>[OPEN-FONT-FORMAT]
    <dd><a
     href="http://www.iso.org/iso/home/store/catalogue_ics/catalogue_detail_ics.htm?csnumber=52136"><cite>Information
     technology — Coding of audio-visual objects — Part 22: Open Font
     Format.</cite></a> International Organization for Standardization.
     ISO/IEC 14496-22:2009. URL: <a
     href="http://www.iso.org/iso/home/store/catalogue_ics/catalogue_detail_ics.htm?csnumber=52136">http://www.iso.org/iso/home/store/catalogue_ics/catalogue_detail_ics.htm?csnumber=52136</a>
     </dd>
    <!---->
    <dt id=OPENTYPE>[OPENTYPE]
    <dd><a
     href="http://www.microsoft.com/typography/otspec/default.htm"><cite>OpenType
     specification.</cite></a> Microsoft. URL: <a
     href="http://www.microsoft.com/typography/otspec/default.htm">http://www.microsoft.com/typography/otspec/default.htm</a>
     </dd>
    <!---->
    <dt id=OPENTYPE-FEATURES>[OPENTYPE-FEATURES]
    <dd><a
     href="http://www.microsoft.com/typography/otspec/featurelist.htm"><cite>OpenType
     feature registry.</cite></a> Microsoft. URL: <a
     href="http://www.microsoft.com/typography/otspec/featurelist.htm">http://www.microsoft.com/typography/otspec/featurelist.htm</a>
     </dd>
    <!---->
    <dt id=RFC2119>[RFC2119]
    <dd>S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key
     words for use in RFCs to Indicate Requirement Levels.</cite></a> Internet
     RFC 2119. URL: <a
     href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
     </dd>
    <!---->
    <dt id=UAX15>[UAX15]
    <dd>Mark Davis; Ken Whistler. <a
     href="http://www.unicode.org/reports/tr15/"><cite>Unicode Normalization
     Forms.</cite></a> 31 August 2012. Unicode Standard Annex #15. URL: <a
     href="http://www.unicode.org/reports/tr15/">http://www.unicode.org/reports/tr15/</a>
     </dd>
    <!---->
    <dt id=UAX29>[UAX29]
    <dd>Mark Davis. <a
     href="http://www.unicode.org/reports/tr29/"><cite>Unicode Text
     Segmentation.</cite></a> 12 September 2012. Unicode Standard Annex #29.
     URL: <a
     href="http://www.unicode.org/reports/tr29/">http://www.unicode.org/reports/tr29/</a>
     </dd>
    <!---->
    <dt id=UNICODE6>[UNICODE6]
    <dd>The Unicode Consortium. <a
     href="http://www.unicode.org/versions/Unicode6.2.0/"><cite>The Unicode
     Standard, Version 6.2.0.</cite></a> Defined by: The Unicode Standard,
     Version 6.2.0 URL: <a
     href="http://www.unicode.org/versions/Unicode6.2.0/">http://www.unicode.org/versions/Unicode6.2.0/</a>
     </dd>
    <!---->
   </dl>
   <!--end-normative-->
   <!--{{!CSS21}}-->
   <!--{{!CSS3VAL}}-->
   <!--{{!OPENTYPE}}-->
   <!--{{!OPENTYPE-FEATURES}}-->
   <!--{{!OPEN-FONT-FORMAT}}-->
   <!--{{!UNICODE6}}-->
   <!--{{!UAX15}}-->
   <!--{{!UAX29}}-->
   <!--{{!CORS}}-->
   <!--{{!HTML5}}-->
   <!--{{!CHARMOD}}-->
   <h3 class=no-num id=other-references>Other References</h3>
   <!--begin-informative-->
   <!-- Sorted by label -->
   <dl class=bibliography>
    <dd style="display: none"><!-- keeps the doc valid if the DL is empty -->
     <!---->
    <dt id=AAT-FEATURES>[AAT-FEATURES]
    <dd><a href="http://developer.apple.com/fonts/registry/"><cite>Apple
     Advanced Typography font feature registry.</cite></a> Apple. URL: <a
     href="http://developer.apple.com/fonts/registry/">http://developer.apple.com/fonts/registry/</a>
     </dd>
    <!---->
    <dt id=ARABIC-TYPO>[ARABIC-TYPO]
    <dd>Huda Smitshuijzen AbiFares. <cite>Arabic Typography: A Comprehensive
     Sourcebook.</cite> Saqi Books. 2001. ISBN 0-86356-347-3.</dd>
    <!---->
    <dt id=CHARMOD-NORM>[CHARMOD-NORM]
    <dd>François Yergeau; et al. <a
     href="http://www.w3.org/TR/2012/WD-charmod-norm-20120501/"><cite>Character
     Model for the World Wide Web 1.0: Normalization.</cite></a> 1 May 2012.
     W3C Working Draft. (Work in progress.) URL: <a
     href="http://www.w3.org/TR/2012/WD-charmod-norm-20120501/">http://www.w3.org/TR/2012/WD-charmod-norm-20120501/</a>
     </dd>
    <!---->
    <dt id=CJKV-INFO-PROCESSING>[CJKV-INFO-PROCESSING]
    <dd>Ken Lunde. <cite>CJKV Information Processing, Second Edition.</cite>
     O'Reilly Media, Inc. 2009. ISBN 0-596-51447-1.</dd>
    <!---->
    <dt id=CSS3-CONDITIONAL>[CSS3-CONDITIONAL]
    <dd>L. David Baron. <a
     href="http://www.w3.org/TR/2013/CR-css3-conditional-20130404/"><cite>CSS
     Conditional Rules Module Level 3.</cite></a> 4 April 2013. W3C Candidate
     Recommendation. (Work in progress.) URL: <a
     href="http://www.w3.org/TR/2013/CR-css3-conditional-20130404/">http://www.w3.org/TR/2013/CR-css3-conditional-20130404/</a>
     </dd>
    <!---->
    <dt id=CSS3TEXT>[CSS3TEXT]
    <dd>Elika J. Etemad; Koji Ishii. <a
     href="http://www.w3.org/TR/2012/WD-css3-text-20121113/"><cite>CSS Text
     Module Level 3.</cite></a> 13 November 2012. W3C Working Draft. (Work in
     progress.) URL: <a
     href="http://www.w3.org/TR/2012/WD-css3-text-20121113/">http://www.w3.org/TR/2012/WD-css3-text-20121113/</a>
     </dd>
    <!---->
    <dt id=DIGITAL-TYPOGRAPHY>[DIGITAL-TYPOGRAPHY]
    <dd>Richard Rubinstein. <cite>Digital Typography, An Introduction to Type
     and Composition for Computer System Design.</cite> Addison-Wesley. 1988.
     ISBN 0-201-17633-5.</dd>
    <!---->
    <dt id=DOM-LEVEL-2-STYLE>[DOM-LEVEL-2-STYLE]
    <dd>Chris Wilson; Philippe Le Hégaret; Vidur Apparao. <a
     href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/"><cite>Document
     Object Model (DOM) Level 2 Style Specification.</cite></a> 13 November
 . W3C Recommendation. URL: <a
     href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/">http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/</a>
     </dd>
    <!---->
    <dt id=ELEMTYPO>[ELEMTYPO]
    <dd>Robert Bringhurst. <cite>The Elements of Typographic Style, Version
 .</cite> Hartley &amp; Marks. 2013. ISBN 0-88179-212-8.</dd>
    <!---->
    <dt id=LANGCULTTYPE>[LANGCULTTYPE]
    <dd>John D. Berry, Ed. <cite>Language Culture Type.</cite> Graphis. 2001.
     ISBN 1-932026-01-0.</dd>
    <!---->
    <dt id=OPENTYPE-FONT-GUIDE>[OPENTYPE-FONT-GUIDE]
    <dd><a
     href="https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf"><cite>OpenType
     User Guide.</cite></a> FontShop International. URL: <a
     href="https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf">https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf</a>
     </dd>
    <!---->
    <dt id=RASTER-TRAGEDY>[RASTER-TRAGEDY]
    <dd>Beat Stamm. <a href="http://www.rastertragedy.com/"><cite>The Raster
     Tragedy at Low-Resolution Revisited.</cite></a> 7 December 2011. URL: <a
     href="http://www.rastertragedy.com/">http://www.rastertragedy.com/</a></dd>
    <!---->
    <dt id=WINDOWS-GLYPH-PROC>[WINDOWS-GLYPH-PROC]
    <dd>John Hudson. <a
     href="http://www.microsoft.com/typography/developers/opentype/default.htm"><cite>Windows
     Glyph Processing.</cite></a> Microsoft Typogrraphy. URL: <a
     href="http://www.microsoft.com/typography/developers/opentype/default.htm">http://www.microsoft.com/typography/developers/opentype/default.htm</a>
     </dd>
    <!---->
   </dl>
   <!--end-informative-->
   <!--{{ARABIC-TYPO}}-->
   <!--{{CJKV-INFO-PROCESSING}}-->
   <!--{{DIGITAL-TYPOGRAPHY}}-->
   <!--{{DOM-LEVEL-2-STYLE}}-->
   <!--{{ELEMTYPO}}-->
   <!--{{LANGCULTTYPE}}-->
   <!--{{OPENTYPE-FONT-GUIDE}}-->
   <!--{{RASTER-TRAGEDY}}-->
   <!--{{WINDOWS-GLYPH-PROC}}-->
   <!--{{CHARMOD-NORM}}-->
   <!--{{AAT-FEATURES}}-->
   <!--{{CSS3-CONDITIONAL}}-->
   <!--{{CSS3TEXT}}-->
   <h2 class=no-num id=index>Index</h2>
   <!--begin-index-->
   <ul class=indexlist>
    <li>100...900 weight values, <a href="#font-weight-numeric-values"
     title="100...900 weight values"><strong>3.2</strong></a>
    <li><var>&lt;absolute-size&gt;</var>, <a href="#absolute-size-value"
     title="&lt;absolute-size&gt;"><strong>3.5</strong></a>
    <li><var>&lt;common-lig-values&gt;</var>, <a href="#common-lig-values"
     title="&lt;common-lig-values&gt;"><strong>6.4</strong></a>
    <li><var>&lt;contextual-alt-values&gt;</var>, <a
     href="#contextual-alt-values"
     title="&lt;contextual-alt-values&gt;"><strong>6.4</strong></a>
    <li><var>&lt;discretionary-lig-values&gt;</var>, <a
     href="#discretionary-lig-values"
     title="&lt;discretionary-lig-values&gt;"><strong>6.4</strong></a>
    <li><var>&lt;east-asian-variant-values&gt;</var>, <a
     href="#east-asian-variant-values"
     title="&lt;east-asian-variant-values&gt;"><strong>6.10</strong></a>
    <li><var>&lt;east-asian-width-values&gt;</var>, <a
     href="#east-asian-width-values"
     title="&lt;east-asian-width-values&gt;"><strong>6.10</strong></a>
    <li><var>&lt;family-name&gt;</var>, <a href="#family-name-value"
     title="&lt;family-name&gt;"><strong>3.1</strong></a>
    <li><var>&lt;feature-tag-value&gt;</var>, <a href="#feature-tag-value"
     title="&lt;feature-tag-value&gt;"><strong>6.12</strong></a>
    <li><var>&lt;font-face-name&gt;</var>, <a href="#font-face-name-value"
     title="&lt;font-face-name&gt;"><strong>4.3</strong></a>
    <li><var>&lt;font-variant-css21&gt;</var>, <a
     href="#font-variant-css21-values"
     title="&lt;font-variant-css21&gt;"><strong>3.7</strong></a>
    <li><var>&lt;generic-family&gt;</var>, <a href="#generic-family-value"
     title="&lt;generic-family&gt;"><strong>3.1</strong></a>
    <li><var>&lt;historical-lig-values&gt;</var>, <a
     href="#historical-lig-values"
     title="&lt;historical-lig-values&gt;"><strong>6.4</strong></a>
    <li><var>&lt;length&gt;</var>, <a href="#length-size-value"
     title="&lt;length&gt;"><strong>3.5</strong></a>
    <li><var>&lt;number&gt;</var>, <a href="#aspect-ratio-value"
     title="&lt;number&gt;"><strong>3.6</strong></a>
    <li><var>&lt;numeric-figure-values&gt;</var>, <a
     href="#numeric-figure-values"
     title="&lt;numeric-figure-values&gt;"><strong>6.7</strong></a>
    <li><var>&lt;numeric-fraction-values&gt;</var>, <a
     href="#numeric-fraction-values"
     title="&lt;numeric-fraction-values&gt;"><strong>6.7</strong></a>
    <li><var>&lt;numeric-spacing-values&gt;</var>, <a
     href="#numeric-spacing-values"
     title="&lt;numeric-spacing-values&gt;"><strong>6.7</strong></a>
    <li><var>&lt;percentage&gt;</var>, <a href="#percentage-size-value"
     title="&lt;percentage&gt;"><strong>3.5</strong></a>
    <li><var>&lt;relative-size&gt;</var>, <a href="#relative-size-value"
     title="&lt;relative-size&gt;"><strong>3.5</strong></a>
    <li><var>&lt;string&gt;</var>, <a
     href="#font-language-override-string-value"
     title="&lt;string&gt;"><strong>6.13</strong></a>
    <li><var>&lt;urange&gt;</var>, <a href="#urange-value"
     title="&lt;urange&gt;"><strong>4.5</strong></a>
    <li><code>@font-face</code>, <a href="#at-font-face-rule"
     title="@font-face"><strong>4.1</strong></a>
    <li><code>@font-feature-values</code>, <a
     href="#at-font-feature-values-rule"
     title="@font-feature-values"><strong>6.9</strong></a>
    <li>all-petite-caps, <a href="#all-petite-caps"
     title=all-petite-caps><strong>6.6</strong></a>
    <li>all-small-caps, <a href="#all-small-caps"
     title=all-small-caps><strong>6.6</strong></a>
    <li>annotation, <a href="#annotation"
     title=annotation><strong>6.8</strong></a>
    <li>aspect value, <a href="#aspect-value0" title="aspect
     value"><strong>3.6</strong></a>
    <li>authoring tool, <a href="#authoring-tool" title="authoring
     tool"><strong>#</strong></a>
    <li>auto
     <ul>
      <li>font-kerning, <a href="#font-kerning-auto-value" title="auto,
       font-kerning"><strong>6.3</strong></a>
      <li>font-size-adjust, <a href="#font-size-adjust-auto-value"
       title="auto, font-size-adjust"><strong>3.6</strong></a>
     </ul>
    <li>bold, <a href="#bold" title=bold><strong>3.2</strong></a>
    <li>bolder, <a href="#bolder" title=bolder><strong>3.2</strong></a>
    <li>character map, <a href="#character-map" title="character
     map"><strong>5.2</strong></a>
    <li>character-variant, <a href="#character-variant"
     title=character-variant><strong>6.8</strong></a>
    <li>common-ligatures, <a href="#common-ligatures"
     title=common-ligatures><strong>6.4</strong></a>
    <li>composite face, <a href="#composite-face" title="composite
     face"><strong>5.2</strong></a>
    <li>condensed, <a href="#condensed"
     title=condensed><strong>3.3</strong></a>
    <li>contextual, <a href="#contextual"
     title=contextual><strong>6.4</strong></a>
    <li>CSSFontFaceRule, <a href="#cssfontfacerule"
     title=CSSFontFaceRule><strong>8.1</strong></a>
    <li>CSSFontFeatureValuesRule, <a href="#cssfontfeaturevaluesrule"
     title=CSSFontFeatureValuesRule><strong>8.2</strong></a>
    <li>cursive, definition of, <a href="#cursive0" title="cursive, definition
     of"><strong>#</strong></a>
    <li>default face, <a href="#default-face" title="default
     face"><strong>5.2</strong></a>
    <li>descriptor_declaration, <a href="#descriptordeclaration"
     title="descriptor_declaration"><strong>4.1</strong></a>
    <li>diagonal-fractions, <a href="#diagonal-fractions"
     title=diagonal-fractions><strong>6.7</strong></a>
    <li>discretionary-ligatures, <a href="#discretionary-ligatures"
     title=discretionary-ligatures><strong>6.4</strong></a>
    <li>effective character map, <a href="#effective-character-map"
     title="effective character map"><strong>4.5</strong></a>
    <li>expanded, <a href="#expanded" title=expanded><strong>3.3</strong></a>
    <li>extra-condensed, <a href="#extra-condensed"
     title=extra-condensed><strong>3.3</strong></a>
    <li>extra-expanded, <a href="#extra-expanded"
     title=extra-expanded><strong>3.3</strong></a>
    <li>fantasy, definition of, <a href="#fantasy0" title="fantasy, definition
     of"><strong>#</strong></a>
    <li>feature_type, <a href="#featuretype"
     title="feature_type"><strong>6.9.1</strong></a>
    <li>feature_value_block, <a href="#featurevalueblock"
     title="feature_value_block"><strong>6.9.1</strong></a>
    <li>feature_value_definition, <a href="#featurevaluedefinition"
     title="feature_value_definition"><strong>6.9.1</strong></a>
    <li>first available font, <a href="#first-available-font" title="first
     available font"><strong>5.2</strong></a>
    <li>font, <a href="#propdef-font" title=font><strong>3.7</strong></a>
    <li>font specific, <a href="#font-specific" title="font
     specific"><strong>6.8</strong></a>
    <li>font-family
     <ul>
      <li>descriptor, <a href="#descdef-font-family" title="font-family,
       descriptor"><strong>4.2</strong></a>
      <li>property, <a href="#propdef-font-family" title="font-family,
       property"><strong>3.1</strong></a>
     </ul>
    <li>font-feature-settings
     <ul>
      <li>descriptor, <a href="#descdef-font-feature-settings"
       title="font-feature-settings, descriptor"><strong>4.7</strong></a>
      <li>property, <a href="#propdef-font-feature-settings"
       title="font-feature-settings, property"><strong>6.12</strong></a>
     </ul>
    <li>font-kerning, <a href="#propdef-font-kerning"
     title=font-kerning><strong>6.3</strong></a>
    <li>font-language-override, <a href="#propdef-font-language-override"
     title=font-language-override><strong>6.13</strong></a>
    <li>font-size, <a href="#propdef-font-size"
     title=font-size><strong>3.5</strong></a>
    <li>font-size-adjust, <a href="#propdef-font-size-adjust"
     title=font-size-adjust><strong>3.6</strong></a>
    <li>font-stretch
     <ul>
      <li>descriptor, <a href="#descdef-font-stretch" title="font-stretch,
       descriptor"><strong>4.4</strong></a>
      <li>property, <a href="#propdef-font-stretch" title="font-stretch,
       property"><strong>3.3</strong></a>
     </ul>
    <li>font-style
     <ul>
      <li>descriptor, <a href="#descdef-font-style" title="font-style,
       descriptor"><strong>4.4</strong></a>
      <li>property, <a href="#propdef-font-style" title="font-style,
       property"><strong>3.4</strong></a>
     </ul>
    <li>font-synthesis, <a href="#propdef-font-synthesis"
     title=font-synthesis><strong>3.8</strong></a>
    <li>font-variant
     <ul>
      <li>descriptor, <a href="#descdef-font-variant" title="font-variant,
       descriptor"><strong>4.7</strong></a>
      <li>property, <a href="#propdef-font-variant" title="font-variant,
       property"><strong>6.11</strong></a>
     </ul>
    <li>font-variant-alternates, <a href="#propdef-font-variant-alternates"
     title=font-variant-alternates><strong>6.8</strong></a>
    <li>font-variant-caps, <a href="#propdef-font-variant-caps"
     title=font-variant-caps><strong>6.6</strong></a>
    <li>font-variant-east-asian, <a href="#propdef-font-variant-east-asian"
     title=font-variant-east-asian><strong>6.10</strong></a>
    <li>font-variant-ligatures, <a href="#propdef-font-variant-ligatures"
     title=font-variant-ligatures><strong>6.4</strong></a>
    <li>font-variant-numeric, <a href="#propdef-font-variant-numeric"
     title=font-variant-numeric><strong>6.7</strong></a>
    <li>font-variant-position, <a href="#propdef-font-variant-position"
     title=font-variant-position><strong>6.5</strong></a>
    <li>font-weight
     <ul>
      <li>descriptor, <a href="#descdef-font-weight" title="font-weight,
       descriptor"><strong>4.4</strong></a>
      <li>property, <a href="#propdef-font-weight" title="font-weight,
       property"><strong>3.2</strong></a>
     </ul>
    <li>font_face_rule, <a href="#fontfacerule"
     title="font_face_rule"><strong>4.1</strong></a>
    <li>FONT_FACE_SYM, <a href="#fontfacesym"
     title="FONT_FACE_SYM"><strong>4.1</strong></a>
    <li>font_family_name, <a href="#fontfamilyname"
     title="font_family_name"><strong>6.9.1</strong></a>
    <li>font_family_name_list, <a href="#fontfamilynamelist"
     title="font_family_name_list"><strong>6.9.1</strong></a>
    <li>font_feature_values_rule, <a href="#fontfeaturevaluesrule"
     title="font_feature_values_rule"><strong>6.9.1</strong></a>
    <li>FONT_FEATURE_VALUES_SYM, <a href="#fontfeaturevaluessym"
     title="FONT_FEATURE_VALUES_SYM"><strong>6.9.1</strong></a>
    <li>full-width, <a href="#full-width"
     title=full-width><strong>6.10</strong></a>
    <li>historical-forms, <a href="#historical-forms"
     title=historical-forms><strong>6.8</strong></a>
    <li>historical-ligatures, <a href="#historical-ligatures"
     title=historical-ligatures><strong>6.4</strong></a>
    <li>italic, <a href="#italic" title=italic><strong>3.4</strong></a>
    <li>jis04, <a href="#jis04" title=jis04><strong>6.10</strong></a>
    <li>jis78, <a href="#jis78" title=jis78><strong>6.10</strong></a>
    <li>jis83, <a href="#jis83" title=jis83><strong>6.10</strong></a>
    <li>jis90, <a href="#jis90" title=jis90><strong>6.10</strong></a>
    <li>lighter, <a href="#lighter" title=lighter><strong>3.2</strong></a>
    <li>lining-nums, <a href="#lining-nums"
     title=lining-nums><strong>6.7</strong></a>
    <li>monospace, definition of, <a href="#monospace0" title="monospace,
     definition of"><strong>#</strong></a>
    <li>no-common-ligatures, <a href="#no-common-ligatures"
     title=no-common-ligatures><strong>6.4</strong></a>
    <li>no-contextual, <a href="#no-contextual"
     title=no-contextual><strong>6.4</strong></a>
    <li>no-discretionary-ligatures, <a href="#no-discretionary-ligatures"
     title=no-discretionary-ligatures><strong>6.4</strong></a>
    <li>no-historical-ligatures, <a href="#no-historical-ligatures"
     title=no-historical-ligatures><strong>6.4</strong></a>
    <li>none
     <ul>
      <li>font-kerning, <a href="#font-kerning-none-value" title="none,
       font-kerning"><strong>6.3</strong></a>
      <li>font-size-adjust, <a href="#font-size-adjust-none-value"
       title="none, font-size-adjust"><strong>3.6</strong></a>
      <li>font-variant, <a href="#font-variant-none-value" title="none,
       font-variant"><strong>6.11</strong></a>
      <li>font-variant-ligatures, <a href="#font-variant-ligatures-none-value"
       title="none, font-variant-ligatures"><strong>6.4</strong></a>
     </ul>
    <li>normal
     <ul>
      <li>font-feature-settings, <a href="#font-feature-settings-normal-value"
       title="normal, font-feature-settings"><strong>6.12</strong></a>
      <li>font-kerning, <a href="#font-kerning-normal-value" title="normal,
       font-kerning"><strong>6.3</strong></a>
      <li>font-language-override, <a
       href="#font-language-override-normal-value" title="normal,
       font-language-override"><strong>6.13</strong></a>
      <li>font-stretch, <a href="#font-stretch-normal-value" title="normal,
       font-stretch"><strong>3.3</strong></a>
      <li>font-style, <a href="#font-style-normal-value" title="normal,
       font-style"><strong>3.4</strong></a>
      <li>font-variant, <a href="#font-variant-normal-value" title="normal,
       font-variant"><strong>6.11</strong></a>
      <li>font-variant-alternates, <a
       href="#font-variant-alternates-normal-value" title="normal,
       font-variant-alternates"><strong>6.8</strong></a>
      <li>font-variant-caps, <a href="#font-variant-caps-normal-value"
       title="normal, font-variant-caps"><strong>6.6</strong></a>
      <li>font-variant-east-asian, <a
       href="#font-variant-east-asian-normal-value" title="normal,
       font-variant-east-asian"><strong>6.10</strong></a>
      <li>font-variant-ligatures, <a
       href="#font-variant-ligatures-normal-value" title="normal,
       font-variant-ligatures"><strong>6.4</strong></a>
      <li>font-variant-numeric, <a href="#font-variant-numeric-normal-value"
       title="normal, font-variant-numeric"><strong>6.7</strong></a>
      <li>font-variant-position, <a href="#font-variant-position-normal-value"
       title="normal, font-variant-position"><strong>6.5</strong></a>
      <li>font-weight, <a href="#font-weight-normal-value" title="normal,
       font-weight"><strong>3.2</strong></a>
     </ul>
    <li>oblique, <a href="#oblique" title=oblique><strong>3.4</strong></a>
    <li>oldstyle-nums, <a href="#oldstyle-nums"
     title=oldstyle-nums><strong>6.7</strong></a>
    <li>ordinal, <a href="#ordinal" title=ordinal><strong>6.7</strong></a>
    <li>ornaments, <a href="#ornaments"
     title=ornaments><strong>6.8</strong></a>
    <li>petite-caps, <a href="#petite-caps"
     title=petite-caps><strong>6.6</strong></a>
    <li>proportional-nums, <a href="#proportional-nums"
     title=proportional-nums><strong>6.7</strong></a>
    <li>proportional-width, <a href="#proportional-width"
     title=proportional-width><strong>6.10</strong></a>
    <li>renderer, <a href="#renderer" title=renderer><strong>#</strong></a>
    <li>ruby, <a href="#ruby" title=ruby><strong>6.10</strong></a>
    <li>sans-serif, definition of, <a href="#sans-serif0" title="sans-serif,
     definition of"><strong>#</strong></a>
    <li>semi-condensed, <a href="#semi-condensed-"
     title=semi-condensed><strong>3.3</strong></a>
    <li>semi-expanded, <a href="#semi-expanded"
     title=semi-expanded><strong>3.3</strong></a>
    <li>serif, definition of, <a href="#serif0" title="serif, definition
     of"><strong>#</strong></a>
    <li>simplified, <a href="#simplified"
     title=simplified><strong>6.10</strong></a>
    <li>slashed-zero, <a href="#slashed-zero"
     title=slashed-zero><strong>6.7</strong></a>
    <li>small-caps, <a href="#small-caps"
     title=small-caps><strong>6.6</strong></a>
    <li>src, <a href="#descdef-src" title=src><strong>4.3</strong></a>
    <li>stacked-fractions, <a href="#stacked-fractions"
     title=stacked-fractions><strong>6.7</strong></a>
    <li>style sheet
     <ul>
      <li>as conformance class, <a href="#style-sheet" title="style sheet, as
       conformance class"><strong>#</strong></a>
     </ul>
    <li>styleset, <a href="#styleset" title=styleset><strong>6.8</strong></a>
    <li>stylistic, <a href="#stylistic"
     title=stylistic><strong>6.8</strong></a>
    <li>sub, <a href="#sub" title=sub><strong>6.5</strong></a>
    <li>super, <a href="#super" title=super><strong>6.5</strong></a>
    <li>support, <a href="#support" title=support><strong>5.2</strong></a>
    <li>swash, <a href="#swash" title=swash><strong>6.8</strong></a>
    <li>system font fallback, <a href="#system-font-fallback" title="system
     font fallback"><strong>5.2</strong></a>
    <li>tabular-nums, <a href="#tabular-nums"
     title=tabular-nums><strong>6.7</strong></a>
    <li>titling-caps, <a href="#titling-caps"
     title=titling-caps><strong>6.6</strong></a>
    <li>traditional, <a href="#traditional"
     title=traditional><strong>6.10</strong></a>
    <li>ultra-condensed, <a href="#ultra-condensed"
     title=ultra-condensed><strong>3.3</strong></a>
    <li>ultra-expanded, <a href="#ultra-expanded"
     title=ultra-expanded><strong>3.3</strong></a>
    <li>unicase, <a href="#unicase" title=unicase><strong>6.6</strong></a>
    <li>unicode-range, <a href="#descdef-unicode-range"
     title=unicode-range><strong>4.5</strong></a>
    <li>weight, <a href="#weight" title=weight><strong>2</strong></a>
    <li>width, <a href="#width" title=width><strong>2</strong></a>
   </ul>
   <!--end-index-->
   <h2 class=no-num id=property-index>Property index</h2>
   <!--begin-properties-->
   <table class=proptable>
    <thead>
     <tr>
      <th>Property
      <th>Values
      <th>Initial
      <th>Applies to
      <th>Inh.
      <th>Percentages
      <th>Media
    <tbody>
     <tr>
      <th><a class=property href="#propdef-font">font</a>
      <td>[ [ &lt;‘font-style’&gt; || &lt;font-variant-css21&gt; ||
       &lt;‘font-weight’&gt; || &lt;‘font-stretch’ ]?
       &lt;‘font-size’&gt; [ / &lt;‘line-height’&gt; ]?
       &lt;‘font-family’&gt; ] | caption | icon | menu | message-box |
       small-caption | status-bar
      <td>see individual properties
      <td>all elements
      <td>yes
      <td>see individual properties
      <td>visual
     <tr>
      <th><span class=property>font-family</span>
      <td>[ &lt;family-name&gt; | &lt;generic-family&gt; ] #
      <td>depends on user agent
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><span class=property>font-feature-settings</span>
      <td>normal | &lt;feature-tag-value&gt; #
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#propdef-font-kerning">font-kerning</a>
      <td>auto | normal | none
      <td>auto
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-language-override">font-language-override</a>
      <td>normal | &lt;string&gt;
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#propdef-font-size">font-size</a>
      <td>&lt;absolute-size&gt; | &lt;relative-size&gt; | &lt;length&gt; |
       &lt;percentage&gt;
      <td>medium
      <td>all elements
      <td>yes
      <td>refer to parent element's font size
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-size-adjust">font-size-adjust</a>
      <td>none | auto | &lt;number&gt;
      <td>none
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><span class=property>font-stretch</span>
      <td>normal | ultra-condensed | extra-condensed | condensed |
       semi-condensed | semi-expanded | expanded | extra-expanded |
       ultra-expanded
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><span class=property>font-style</span>
      <td>normal | italic | oblique
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#propdef-font-synthesis">font-synthesis</a>
      <td>none | [ weight || style ]
      <td>weight style
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><span class=property>font-variant</span>
      <td>normal | none | [ &lt;common-lig-values&gt; ||
       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
       || historical-forms || styleset(&lt;feature-value-name&gt; #) ||
       character-variant(&lt;feature-value-name&gt; #) ||
       swash(&lt;feature-value-name&gt;) ||
       ornaments(&lt;feature-value-name&gt;) ||
       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
       ruby ]
      <td>normal
      <td>all elements
      <td>yes
      <td>see individual properties
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-alternates">font-variant-alternates</a>
      <td>normal | [ stylistic(&lt;feature-value-name&gt;) || historical-forms
       || styleset(&lt;feature-value-name&gt; #) ||
       character-variant(&lt;feature-value-name&gt; #) ||
       swash(&lt;feature-value-name&gt;) ||
       ornaments(&lt;feature-value-name&gt;) ||
       annotation(&lt;feature-value-name&gt;) ]
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-caps">font-variant-caps</a>
      <td>normal | small-caps | all-small-caps | petite-caps | all-petite-caps
       | unicase | titling-caps
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-east-asian">font-variant-east-asian</a>
      <td>normal | [ &lt;east-asian-variant-values&gt; ||
       &lt;east-asian-width-values&gt; || ruby ]
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-ligatures">font-variant-ligatures</a>
      <td>normal | none | [ &lt;common-lig-values&gt; ||
       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
       &lt;contextual-alt-values&gt; ]
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-numeric">font-variant-numeric</a>
      <td>normal | [ &lt;numeric-figure-values&gt; ||
       &lt;numeric-spacing-values&gt; || &lt;numeric-fraction-values&gt; ||
       ordinal || slashed-zero ]
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-position">font-variant-position</a>
      <td>normal | sub | super
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><span class=property>font-weight</span>
      <td>normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600
       | 700 | 800 | 900
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
   </table>
   <!--end-properties-->
   <!--begin-descriptors-->
   <table class=proptable>
    <thead>
     <tr>
      <th>Descriptor
      <th>Value
      <th>Initial
      <th>Percentages
      <th>Media
    <tbody>
     <tr>
      <th><span class=property>font-family</span>
      <td>&lt;family-name&gt;
      <td>N/A
     <tr>
      <th><span class=property>font-feature-settings</span>
      <td>normal | &lt;feature-tag-value&gt; #
      <td>normal
     <tr>
      <th><span class=property>font-stretch</span>
      <td>normal | ultra-condensed | extra-condensed | condensed |
       semi-condensed | semi-expanded | expanded | extra-expanded |
       ultra-expanded
      <td>normal
     <tr>
      <th><span class=property>font-style</span>
      <td>normal | italic | oblique
      <td>normal
     <tr>
      <th><span class=property>font-variant</span>
      <td>normal | none | [ &lt;common-lig-values&gt; ||
       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
       || historical-forms || styleset(&lt;feature-value-name&gt; #) ||
       character-variant(&lt;feature-value-name&gt; #) ||
       swash(&lt;feature-value-name&gt;) ||
       ornaments(&lt;feature-value-name&gt;) ||
       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
       ruby ]
      <td>normal
     <tr>
      <th><span class=property>font-weight</span>
      <td>normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
      <td>normal
     <tr>
      <th><a class=property href="#descdef-src">src</a>
      <td>[ &lt;url> [format(&lt;string> #)]? | &lt;font-face-name&gt; ] #
      <td>N/A
     <tr>
      <th><a class=property href="#descdef-unicode-range">unicode-range</a>
      <td>&lt;urange&gt; #
      <td>U+0-10FFFF
   </table>
   <!--end-descriptors-->
   <script type="text/javascript">
 window.onload = function () {
   if (!("devicePixelRatio" in window && window.devicePixelRatio > 1)) return;
   var i, hiresElements = document.getElementsByClassName("hires");
   for (i = 0; i < hiresElements.length; i++) {
     var h = hiresElements[i];
     if (h.tagName != "IMG") continue;
     var src = h.getAttribute("src");
     var src2x = src.replace(/\.\w+$/, function(m) { return "@2x" + m; });
     h.src = src2x;
   }
 }
 </script>
 </html>
 <!-- Keep this comment at the end of the file
 Local variables:
 mode: sgml
 sgml-declaration:"~/SGML/HTML4.decl"
 sgml-default-doctype-name:"html"
 sgml-minimize-attributes:t
 sgml-nofill-elements:("pre" "style" "br")
 sgml-live-element-indicator:t
 sgml-omittag:nil
 sgml-shorttag:nil
 sgml-namecase-general:t
 sgml-general-insert-case:lower
 sgml-always-quote-attributes:t
 sgml-indent-step:nil
 sgml-indent-data:t
 sgml-parent-document:nil
 sgml-exposed-tags:nil
 sgml-local-catalogs:nil
 sgml-local-ecat-files:nil
 End:
 -->
 <!--
 to do:
 - wording of OpenType family name handling
 - handling combining sequences in the font matching algorithm
 - fix-up fi ligature example
 -->

Mercurial > drafts / annotate

css-fonts/Fonts.html@77d3edf17f8c (annotated)

css-fonts/Fonts.html