css3-values/Overview.html@324c6ef7c447
css3-values/Overview.html
Wed, 10 Aug 2011 23:45:29 +0000
- author
- Elika Etemad <fantasai.cvs@inkedblade.net>
- date
- Wed, 10 Aug 2011 23:45:29 +0000
- changeset 3292
- 324c6ef7c447
- parent 3291
- 8e1babb965e4
- child 3293
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- -rw-r--r--
Generic Datatype Reorganization Part V: Strings and URLs
Also, create a cleaner split between this module and syntax.
1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
2 "http://www.w3.org/TR/html4/strict.dtd">
4 <html lang=en>
5 <head><meta content="text/html; charset=iso-8859-1" http-equiv=Content-Type>
7 <title>CSS3 Values and Units</title>
9 <style type="text/css">
10 .issue { color: red }
11 table { border-collapse: collapse; border: 1px solid black; margin: 1em 0 }
12 th, td { border: 1px solid black; padding: 0.2em; text-align: left }
13 tt.declaration { white-space: nowrap }
14 .del { text-decoration: line-through}
15 .say { font-style: italic }
16 .value { font: inherit; white-space: pre-wrap; margin: 0; padding: 0; }
17 #propvalues td { text-align: right; }
18 #propvalues td + td { text-align: left; }
19 p { text-indent: 0 !important; margin: 1em 0 !important; }
20 </style>
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22 <link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
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25 <body>
26 <div class=head> <!--begin-logo-->
27 <p><a href="http://www.w3.org/"><img alt=W3C height=48
28 src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->
30 <h1 id=css3-template>CSS3 Values and Units</h1>
32 <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 10 August 2011</h2>
34 <dl>
35 <dt>This version:
37 <dd><a
38 href="http://www.w3.org/TR/2011/ED-css3-values-20110810/">http://www.w3.org/TR/2011/ED-css3-values-20110810/</a>
40 <dt>Latest version:
42 <dd><a
43 href="http://www.w3.org/TR/css3-values">http://www.w3.org/TR/css3-values</a>
45 <dt>Previous version:
47 <dd><a
48 href="http://www.w3.org/TR/2005/WD-css3-values-20050726">http://www.w3.org/TR/2005/WD-css3-values-20050726</a>
50 <dt>Editors:
52 <dd>Håkon Wium Lie, Opera Software <howcome@opera.com>
54 <dd>Tab Atkins, Google
56 <dd>Elika J. Etemad, Invited Expert
57 </dl>
58 <!--begin-copyright-->
59 <p class=copyright><a
60 href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
61 rel=license>Copyright</a> © 2011 <a
62 href="http://www.w3.org/"><acronym title="World Wide Web
63 Consortium">W3C</acronym></a><sup>®</sup> (<a
64 href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute
65 of Technology">MIT</acronym></a>, <a href="http://www.ercim.eu/"><acronym
66 title="European Research Consortium for Informatics and
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68 href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a
69 href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
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71 href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
72 and <a
73 href="http://www.w3.org/Consortium/Legal/copyright-documents">document
74 use</a> rules apply.</p>
75 <!--end-copyright-->
76 <hr title="Separator for header">
77 </div>
79 <h2 class="no-num no-toc" id=abstract>Abstract</h2>
81 <p>This CSS3 module describes the various values and units that CSS
82 properties accept. Also, it describes how values are computed from
83 "specified" through "computed" and "used" into "actual" values. The main
84 purpose of this module is to define common values and units in one
85 specification which can be referred to by other modules. As such, it does
86 not make sense to claim conformance with this module alone.
88 <h2 class="no-num no-toc" id=status>Status of this document</h2>
89 <!--begin-status-->
91 <p>This is a public copy of the editors' draft. It is provided for
92 discussion only and may change at any moment. Its publication here does
93 not imply endorsement of its contents by W3C. Don't cite this document
94 other than as work in progress.
96 <p>The (<a
97 href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
98 mailing list <a
99 href="mailto:www-style@w3.org?Subject=%5Bcss3-values%5D%20PUT%20SUBJECT%20HERE">
100 www-style@w3.org</a> (see <a
101 href="http://www.w3.org/Mail/Request">instructions</a>) is preferred for
102 discussion of this specification. When sending e-mail, please put the text
103 “css3-values” in the subject, preferably like this:
104 “[<!---->css3-values<!---->] <em>…summary of
105 comment…</em>”
107 <p>This document was produced by the <a href="/Style/CSS/members">CSS
108 Working Group</a> (part of the <a href="/Style/">Style Activity</a>).
110 <p>This document was produced by a group operating under the <a
111 href="/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent
112 Policy</a>. W3C maintains a <a href="/2004/01/pp-impl/32061/status"
113 rel=disclosure>public list of any patent disclosures</a> made in
114 connection with the deliverables of the group; that page also includes
115 instructions for disclosing a patent. An individual who has actual
116 knowledge of a patent which the individual believes contains <a
117 href="/Consortium/Patent-Policy-20040205/#def-essential">Essential
118 Claim(s)</a> must disclose the information in accordance with <a
119 href="/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the
120 W3C Patent Policy</a>.</p>
121 <!--end-status-->
123 <p>All features described in this specification that also exist in CSS 2.1
124 <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> are intended
125 to be backwards compatible. In case of conflict between this draft and
126 CSS 2.1 <a href="#CSS21"
127 rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>, CSS 2.1 probably
128 represents the intention of the CSS WG better than this draft (other than
129 on values and units that are new to CSS3).
131 <p>This is a draft of a <a href="http://www.w3.org/TR/css3-roadmap/">module
132 of CSS level 3</a>. It will probably be bundled with some other modules
133 before it becomes a <a href="http://www.w3.org/TR/#About">W3C
134 Recommendation</a>.
136 <h2 class="no-num no-toc" id=contents>Table of contents</h2>
137 <!--begin-toc-->
139 <ul class=toc>
140 <li><a href="#introduction"><span class=secno>1. </span>Introduction</a>
141 <ul class=toc>
142 <li><a href="#placement"><span class=secno>1.1. </span> Module
143 Interactions</a>
144 </ul>
146 <li><a href="#value-defs"><span class=secno>2. </span> Value Definition
147 Syntax</a>
148 <ul class=toc>
149 <li><a href="#component-types"><span class=secno>2.1. </span> Component
150 value types</a>
152 <li><a href="#component-combinators"><span class=secno>2.2. </span>
153 Component value combinators</a>
155 <li><a href="#component-multipliers"><span class=secno>2.3. </span>
156 Component value multipliers</a>
158 <li><a href="#component-whitespace"><span class=secno>2.4. </span>
159 Component values and white space</a>
161 <li><a href="#value-examples"><span class=secno>2.5. </span> Property
162 value examples</a>
163 </ul>
165 <li><a href="#syntax-and-terminology"><span class=secno>3. </span>Syntax
166 and terminology</a>
167 <ul class=toc>
168 <li><a href="#functional-notation"><span class=secno>3.1.
169 </span>Functional notation</a>
170 </ul>
172 <li><a href="#textual-values"><span class=secno>4. </span> Textual Data
173 Types</a>
174 <ul class=toc>
175 <li><a href="#keywords"><span class=secno>4.1. </span> Pre-defined
176 Keywords</a>
177 <ul class=toc>
178 <li><a href="#initial-inherit"><span class=secno>4.1.1. </span> The
179 ‘<code class=css>initial</code>’ and ‘<code
180 class=css>inherit</code>’ keywords</a>
181 </ul>
183 <li><a href="#identifiers"><span class=secno>4.2. </span> User-defined
184 Identifiers: the ‘<code
185 class=css><identifier></code>’ type</a>
187 <li><a href="#strings"><span class=secno>4.3. </span> Quoted Strings:
188 the ‘<code class=css><string></code>’ type</a>
190 <li><a href="#urls"><span class=secno>4.4. </span> Resource Locators:
191 the ‘<code class=css><url></code>’ type</a>
192 </ul>
194 <li><a href="#numeric-types"><span class=secno>5. </span> Numeric Data
195 Types</a>
196 <ul class=toc>
197 <li><a href="#integers"><span class=secno>5.1. </span> Integers: the
198 ‘<code class=css><integer></code>’ type</a>
200 <li><a href="#numbers"><span class=secno>5.2. </span> Numbers: the
201 ‘<code class=css><number></code>’ type</a>
203 <li><a href="#percentages"><span class=secno>5.3. </span> Percentages:
204 the ‘<code class=css><percentage></code>’ type</a>
205 </ul>
207 <li><a href="#lengths"><span class=secno>6. </span> Distance Units: the
208 ‘<code class=css><length></code>’ type</a>
209 <ul class=toc>
210 <li><a href="#relative-lengths"><span class=secno>6.1. </span> Relative
211 lengths</a>
212 <ul class=toc>
213 <li><a href="#font-relative-lengths"><span class=secno>6.1.1. </span>
214 Font-relative lengths: the ‘<code class=css>em</code>’,
215 ‘<code class=css>ex</code>’, ‘<code
216 class=css>ch</code>’, ‘<code class=css>rem</code>’
217 units</a>
219 <li><a href="#viewport-relative-lengths"><span class=secno>6.1.2.
220 </span> Viewport-relative lengths: the ‘<code
221 class=css>vw</code>’, ‘<code class=css>vh</code>’,
222 ‘<code class=css>vm</code>’ units</a>
223 </ul>
225 <li><a href="#absolute-lengths"><span class=secno>6.2. </span> Absolute
226 lengths: the ‘<code class=css>cm</code>’, ‘<code
227 class=css>mm</code>’, ‘<code class=css>in</code>’,
228 ‘<code class=css>pt</code>’, ‘<code
229 class=css>pc</code>’, ‘<code class=css>px</code>’
230 units </a>
231 </ul>
233 <li><a href="#other-units"><span class=secno>7. </span> Other Units</a>
234 <ul class=toc>
235 <li><a href="#angles"><span class=secno>7.1. </span> Angles: the
236 ‘<code class=css><angle></code>’ type and
237 ‘<code class=css>deg</code>’, ‘<code
238 class=css>grad</code>’, ‘<code class=css>rad</code>’,
239 ‘<code class=css>turn</code>’ units</a>
241 <li><a href="#time"><span class=secno>7.2. </span> Times: the
242 ‘<code class=css><time></code>’ type and ‘<code
243 class=css>s</code>’, ‘<code class=css>ms</code>’
244 units</a>
246 <li><a href="#frequencies-the-ltfrequencygt-type-and-h"><span
247 class=secno>7.3. </span>Frequencies: the ‘<code
248 class=css><frequency></code>’ type and ‘<code
249 class=css>Hz</code>’, ‘<code class=css>kHz</code>’
250 units</a>
251 <ul class=toc>
252 <li><a href="#the-calc-min-and-max-functions"><span class=secno>7.3.1.
253 </span>The ‘<code class=property>calc</code>’,
254 ‘<code class=property>min</code>’ and ‘<code
255 class=property>max</code>’ functions</a>
256 </ul>
258 <li><a href="#ltcolorgt"><span class=secno>7.4. </span><color></a>
261 <li><a href="#ltattrgt"><span class=secno>7.5. </span><attr></a>
263 <li><a href="#ltimagegt"><span class=secno>7.6. </span><image></a>
266 <li><a href="#ltfractiongt"><span class=secno>7.7.
267 </span><fraction></a>
268 <ul class=toc>
269 <li><a href="#the-fr-unit"><span class=secno>7.7.1. </span>The
270 ‘<code class=property>fr</code>’ unit</a>
271 </ul>
273 <li><a href="#ltgridgt"><span class=secno>7.8. </span><grid></a>
274 <ul class=toc>
275 <li><a href="#the-gr-unit"><span class=secno>7.8.1. </span>The
276 ‘<code class=property>gr</code>’ unit</a>
277 </ul>
278 </ul>
280 <li><a href="#specified-computed-used-and-actual-value"><span
281 class=secno>8. </span>Specified, computed, used, and actual values</a>
282 <ul class=toc>
283 <li><a href="#finding-the-specified-value"><span class=secno>8.1.
284 </span>Finding the specified value</a>
286 <li><a href="#finding-the-computed-value"><span class=secno>8.2.
287 </span>Finding the computed value</a>
289 <li><a href="#finding-the-used-value"><span class=secno>8.3.
290 </span>Finding the used value</a>
292 <li><a href="#finding-the-actual-value"><span class=secno>8.4.
293 </span>Finding the actual value</a>
294 </ul>
296 <li class=no-num><a href="#acknowledgments">Acknowledgments</a>
298 <li class=no-num><a href="#references">References</a>
299 <ul class=toc>
300 <li class=no-num><a href="#normative-references">Normative
301 references</a>
303 <li class=no-num><a href="#other-references">Other references</a>
304 </ul>
306 <li class=no-num><a href="#index">Index</a>
307 </ul>
308 <!--end-toc-->
310 <h2 id=introduction><span class=secno>1. </span>Introduction</h2>
312 <p>The value definition field of each CSS property can contain keywords,
313 data types (which appear between ‘<code class=css><</code>’
314 and ‘<code class=css>></code>’), and information on how they
315 can be combined. Generic data types (<a
316 href="#length-value"><code><length></code></a> being the most widely
317 used) that can be used by many properties are described in this
318 specification, while more specific data types (e.g.,
319 <code><border-width></code>) are described in the corresponding
320 modules. </code>
322 <h3 id=placement><span class=secno>1.1. </span> Module Interactions</h3>
324 <p>This module replaces and extends the data type definitions in <a
325 href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> sections <a
326 href="http://www.w3.org/TR/CSS21/about.html#value-defs">1.4.2.1</a>, <a
327 href="http://www.w3.org/TR/CSS21/syndata.html#values">4.3</a>, and <a
328 href="http://www.w3.org/TR/CSS21/aural.html#aural-intro">A.2</a>.
330 <h2 id=value-defs><span class=secno>2. </span> Value Definition Syntax</h2>
332 <p>The syntax described here is used to define the set of valid values for
333 CSS properties. A property value can have one or more components.
335 <h3 id=component-types><span class=secno>2.1. </span> Component value types</h3>
337 <p>Component value types are designated in several ways:
339 <ol>
340 <li><a href="#keyword">keyword</a> values (such as ‘<code
341 class=css>auto</code>’, ‘<code class=css>disc</code>’,
342 etc.), which appear literally, without quotes (e.g. <code>auto</code>)
344 <li>basic data types, which appear between ‘<code
345 class=css><</code>’ and ‘<code
346 class=css>></code>’ (e.g., <a
347 href="#length-value"><code><length></code></a>, <a
348 href="#percentage-value"><code><percentage></code></a>, etc.).
350 <li>types that have the same range of values as a property bearing the
351 same name (e.g., <code><'border-width'></code>
352 <code><'background-attachment'></code>, etc.). In this case, the
353 type name is the property name (complete with quotes) between the
354 brackets. Such a type does <em>not</em> include the value ‘<code
355 class=property>inherit</code>’.
357 <li>non-terminals that do not share the same name as a property. In this
358 case, the non-terminal name appears between ‘<code
359 class=css><</code>’ and ‘<code
360 class=css>></code>’, as in <code><spacing></code>. Notice
361 the distinction between <code><border-width></code> and
362 <code><'border-width'></code>: the latter is defined as the value
363 of the ‘<code class=property>border-width</code>’ property,
364 the former requires an explicit expansion elsewhere. The definition of a
365 non-terminal is located near its first appearance in the specification.
366 </ol>
368 <p>Some property value definitions also include the slash (/) and/or the
369 comma (,) as literals. These represent their corresponding tokens.
371 <p>All CSS properties also accept the keyword values ‘<code
372 class=css>inherit</code>’ and ‘<code
373 class=css>initial</code>’ as their property value, but for
374 readability these are not listed explicitly in the property value syntax
375 definitions. These keywords cannot be combined with other component values
376 in same declaration; such a declaration is invalid. For example,
377 ‘<code class=css>background: url(corner.png) no-repeat,
378 inherit;</code>’ is invalid.
380 <h3 id=component-combinators><span class=secno>2.2. </span> Component value
381 combinators</h3>
383 <p>Component values can be arranged into property values as follows:
385 <ul>
386 <li>Several juxtaposed words mean that all of them must occur, in the
387 given order.
389 <li>A double ampersand (&&) separates two or more components, all of which
390 must occur, in any order.
392 <li>A double bar (||) separates two or more options: one or more of them
393 must occur, in any order.
395 <li>A bar (|) separates two or more alternatives: exactly one of them must
396 occur.
398 <li>Brackets ([ ]) are for grouping.
399 </ul>
401 <p>Juxtaposition is stronger than the double ampersand, the double
402 ampersand is stronger than the double bar, and the double bar is stronger
403 than the bar. Thus, the following lines are equivalent:
405 <pre>
406 <!----> a b | c || d && e f
407 <!---->[ a b ] | [ c || [ d && [ e f ]]]</pre>
409 <h3 id=component-multipliers><span class=secno>2.3. </span> Component value
410 multipliers</h3>
412 <p>Every type, keyword, or bracketed group may be followed by one of the
413 following modifiers:
415 <ul>
416 <li>An asterisk (*) indicates that the preceding type, word, or group
417 occurs zero or more times.
419 <li>A plus (+) indicates that the preceding type, word, or group occurs
420 one or more times.
422 <li>A question mark (?) indicates that the preceding type, word, or group
423 is optional.
425 <li>A pair of numbers in curly braces ({<var>A</var>,<var>B</var>})
426 indicates that the preceding type, word, or group occurs at least
427 <var>A</var> and at most <var>B</var> times.
429 <li>A hash mark (#) indicates that the preceding type, word, or group
430 occurs one or more times, separated by comma tokens.
431 </ul>
433 <h3 id=component-whitespace><span class=secno>2.4. </span> Component values
434 and white space</h3>
436 <p>Component values are specified in terms of tokens, as described in <a
437 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">Chapter 4</a>
438 of <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>. As the
439 grammar allows spaces between tokens in the components of the
440 <code>value</code> production, spaces may appear between tokens in
441 property values.
443 <p class=note>Note: In many cases, spaces will in fact be <em>required</em>
444 between tokens in order to distinguish them from each other. For example,
445 the value ‘<code class=css>1em2em</code>’ would be parsed as a
446 single <code>DIMEN</code> token with the number ‘<code
447 class=css>1</code>’ and the identifier ‘<code
448 class=css>em2em</code>’, which is an invalid unit. In this case, a
449 space would be required before the ‘<code class=css>2</code>’
450 to get this parsed as the two lengths ‘<code
451 class=css>1em</code>’ and ‘<code class=css>2em</code>’.
453 <h3 id=value-examples><span class=secno>2.5. </span> Property value
454 examples</h3>
456 <p>Below are some examples of properties with their corresponding value
457 definition fields
459 <div class=example>
460 <table class=data id=propvalues>
461 <thead>
462 <tr>
463 <th>Property
465 <th>Value definition field
467 <th>Example value
469 <tbody>
470 <tr>
471 <td>‘<code class=property>orphans</code>’
473 <td><integer>
475 <td>‘<code class=css>3</code>’
477 <tr>
478 <td>‘<code class=property>text-align</code>’
480 <td>left | right | center | justify
482 <td>‘<code class=css>center</code>’
484 <tr>
485 <td>‘<code class=property>padding-top</code>’
487 <td><length> | <percentage>
489 <td>‘<code class=css>5%</code>’
491 <tr>
492 <td>‘<code class=property>outline-color</code>’
494 <td><color> | invert
496 <td>‘<code class=css>#fefefe</code>’
498 <tr>
499 <td>‘<code class=property>text-decoration</code>’
501 <td>none | underline || overline || line-through || blink
503 <td>‘<code class=css>overline underline</code>’
505 <tr>
506 <td>‘<code class=property>font-family</code>’
508 <td><family-name>#
510 <td>‘<code class=css>"Gill Sans", Futura,
511 sans-serif</code>’
513 <tr>
514 <td>‘<code class=property>border-width</code>’
516 <td>[ <length> | thick | medium | thin ]{1,4}
518 <td>‘<code class=css>2px medium 4px</code>’
520 <tr>
521 <td>‘<code class=property>text-shadow</code>’
523 <td>[ inset? && [ <length>{2,4} && <color>? ] ]# | none
525 <td>‘<code class=css>3px 3px rgba(50%, 50%, 50%, 50%),
526 lemonchiffon 0 0 4px inset</code>’
528 <tr>
529 <td>‘<code class=property>voice-pitch</code>’
531 <td>
532 <pre class=value><frequency> && absolute |
533 <!-- -->[[x-low | low | medium | high | x-high] ||
534 <!-- --> [<frequency> | <semitones> | <percentage>]]</pre>
536 <td>‘<code class=css>-2st x-low</code>’
537 </table>
538 </div>
540 <h2 id=syntax-and-terminology><span class=secno>3. </span>Syntax and
541 terminology</h2>
543 <p>The generic data types described in the next sections use some common
544 syntactic building blocks and terms that are described in this section.
546 <h3 id=functional-notation><span class=secno>3.1. </span>Functional
547 notation</h3>
549 <p>Some values use a <dfn id=functional-notation0>functional notation</dfn>
550 to type values and to and lump values together. The syntax starts with the
551 name of the function followed by a left parenthesis followed by optional
552 whitespace followed by the argument(s) to the functions followed by
553 optional whitespace followed by a right parenthesis. If a function takes
554 more than one argument, the arguments are separated by a comma
555 (‘<code class=css>,</code>’) with optional whitespace before
556 and after the comma.
558 <div class=example> background: url(http://www.example.org/image); color:
559 rgb(100, 200, 50 );</div>
561 <p>Some properties accept space- or comma-separated lists of values. A
562 value that is composed of several values with spaces or commas between
563 them, is called a <dfn id=compound-value>compound value</dfn>. A value
564 that is not a compound value is a <dfn id=simple-value>simple value</dfn>.
567 <h2 id=textual-values><span class=secno>4. </span> Textual Data Types</h2>
569 <p>An <dfn id=identifier>identifier</dfn> is a sequence of characters
570 conforming to the <code>IDENT</code> token in the <a
571 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">grammar</a>.
572 <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> Identifiers
573 cannot be quoted; otherwise they would be interpreted as a string.
575 <h3 id=keywords><span class=secno>4.1. </span> Pre-defined Keywords</h3>
577 <p>In the value definition fields, keywords with a pre-defined meaning
578 appear literally. Keywords are CSS <i>identifiers</i> and are interpreted
579 case-insensitively within the ASCII range (i.e., [a-z] and [A-Z] are
580 equivalent).
582 <div class=example>
583 <p>For example, here is the value definition for the ‘<code
584 class=property>border-collapse</code>’ property:</p>
586 <pre>Value: collapse | separate</pre>
588 <p>And here is an example of its use:</p>
590 <pre>table { border-collapse: separate }</pre>
591 </div>
593 <h4 id=initial-inherit><span class=secno>4.1.1. </span> The ‘<code
594 class=css>initial</code>’ and ‘<code
595 class=css>inherit</code>’ keywords</h4>
597 <p>As defined <a href="#component-types">above</a>, all properties accept
598 the ‘<code class=css>initial</code>’ and ‘<code
599 class=css>inherit</code>’ keywords, which represent value concepts
600 common to all CSS properties.
602 <p>The <dfn id=inherit>‘<code class=css>inherit</code>’</dfn>
603 keyword is <a
604 href="http://www.w3.org/TR/CSS21/cascade.html#value-def-inherit">defined</a>
605 in <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>.
607 <p>The <dfn id=initial>‘<code class=css>initial</code>’</dfn>
608 keyword represents the value that is designated as the property's initial
609 value. <a href="#CSS3CASCADE"
610 rel=biblioentry>[CSS3CASCADE]<!--{{CSS3CASCADE}}--></a>
612 <p class=issue>Should these keywords affect the specified or computed
613 value? See <a
614 href="http://lists.w3.org/Archives/Public/www-style/2011Jan/0075.html">various</a>
615 <a
616 href="http://lists.w3.org/Archives/Public/www-style/2011May/0402.html">issues</a>.
619 <p class=issue>Would it be useful to have a ‘<code
620 class=property>default</code>’ value, defined to be equivalent to <a
621 class=css href="#inherit">‘<code
622 class=property>inherit</code>’</a> for properties that are inherited
623 by default and equivalent to <a class=css href="#initial">‘<code
624 class=property>initial</code>’</a> for properties that are not
625 inherited by default? This might be easier for authors to use than <a
626 class=css href="#initial">‘<code
627 class=property>initial</code>’</a> and <a class=css
628 href="#inherit">‘<code class=property>inherit</code>’</a>
629 since it wouldn't require thinking about whether a property is inherited
630 by default or not (which isn't obvious for some properties, such as
631 text-decoration and visibility).
633 <h3 id=identifiers><span class=secno>4.2. </span> User-defined Identifiers:
634 the ‘<a href="#identifier-value"><code
635 class=css><identifier></code></a>’ type</h3>
637 <p>Some properties accept arbitrary user-defined identifiers as a component
638 value. This generic data type is denoted by <dfn
639 id=identifier-value><code><identifier></code></dfn>, and represents
640 any valid CSS <a href="#identifier"><i>identifier</i></a> that does not
641 otherwise appear as a pre-defined keyword in that property's value
642 definition. Such identifiers are fully case-sensitive, even in the ASCII
643 range (e.g. ‘<code class=css>example</code>’ and ‘<code
644 class=css>EXAMPLE</code>’ are two different, unrelated user-defined
645 identifiers).
647 <h3 id=strings><span class=secno>4.3. </span> Quoted Strings: the ‘<a
648 href="#string-value"><code class=css><string></code></a>’ type</h3>
650 <p>Strings are denoted by <dfn
651 id=string-value><code><string></code></dfn> and consist of a
652 sequence of characters delimited by double quotes or single quotes. They
653 correspond to the <code>STRING</code> token in the <a
654 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">grammar</a>.
655 <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
657 <div class=example>
658 <p>Double quotes cannot occur inside double quotes, unless escaped (as
659 ‘<code class=css>\"</code>’ or as ‘<code
660 class=css>\22</code>’). Analogously for single quotes
661 ("\‘<code class=css>" or "\27"). </code>
663 <pre>
664 <!-- -->content: "this is a ’string'.";
665 <!-- -->content: "this is a \"string\".";
666 <!-- -->content: ‘<code class=css>this is a "string".</code>’;
667 <!-- -->content: ‘<code class=css>this is a \</code>’string\‘<code class=css>.</code>’;</pre>
668 </div>
670 <p>It is possible to break strings over several lines, for aesthetic or
671 other reasons, but in such a case the newline itself has to be escaped
672 with a backslash (\). The newline is subsequently removed from the string.
673 For instance, the following two selectors are exactly the same:
675 <div class=example>
676 <p style="display:none">Example(s):</p>
678 <pre>
679 <!-- -->a[title="a not s\
680 <!-- -->o very long title"] {/*...*/}
681 <!-- -->a[title="a not so very long title"] {/*...*/}</pre>
682 </div>
684 <p>Since a string cannot directly represent a newline, to include a newline
685 in a string, use the escape "\A". (Hexadecimal A is the line feed
686 character in Unicode (U+000A), but represents the generic notion of
687 "newline" in CSS.)
689 <h3 id=urls><span class=secno>4.4. </span> Resource Locators: the ‘<a
690 href="#url-value"><code class=css><url></code></a>’ type</h3>
692 <p>A <dfn id=url>URL</dfn> is a pointer to a resource and is a <a
693 href="http://www.w3.org/TR/CSS21/syndata.html#uri">specially-parsed</a> <a
694 href="#functional-notation">functional notation</a> denoted by <dfn
695 id=url-value><code><url></code></dfn>. It corresponds to the
696 <code>URI</code> token in the <a
697 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">grammar</a>.
698 <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
700 <div class=example>
701 <p>Below is an example of a URL being used as a background image:
703 <pre>body { background: url("http://www.example.com/pinkish.gif") }</pre>
705 <p>The same example can be written without quotes:
707 <pre>body { background: url(http://www.example.com/pinkish.gif) }</pre>
708 </div>
710 <p class=note>Note that in some CSS syntactic contexts (as defined by that
711 context), a URL can be represented as a <a
712 href="#string-value"><code><string></code></a> rather than by <a
713 href="#url-value"><code><URL></code></a>. An example of this is the
714 <a href="http://www.w3.org/TR/CSS21/cascade.html#at-import">‘<code
715 class=css>@import</code>’ rule</a>.
717 <p>Parentheses, whitespace characters, single quotes (') and double
718 quotes (") appearing in a URL must be escaped with a backslash so that the
719 resulting value is a valid <a href="#url"><code>URL</code></a> token, e.g.
720 ‘<code class=css>url(open\(parens)</code>’, ‘<code
721 class=css>url(close\)parens)</code>’. Depending on the type of URL,
722 it might also be possible to write these characters as URI-escapes (where
723 <code>(</code> = <code>%28</code>, <code>)</code> = <code>%29</code>,
724 etc.) as described in <a href="#URI"
725 rel=biblioentry>[URI]<!--{{URI}}--></a>. Alternatively a URL containing
726 such characters may be represented as a quoted <a
727 href="#string">string</a> within the ‘<a href="#url"><code
728 class=css>url()</code></a>’ notation.
730 <p>In order to create modular style sheets that are not dependent on the
731 absolute location of a resource, authors should use relative URIs.
732 Relative URIs (as defined in [[RFC3986]]) are resolved to full URIs using
733 a base URI. RFC 3986, section 3, defines the normative algorithm
734 for this process. For CSS style sheets, the base URI is that of the style
735 sheet, not that of the source document.
737 <div class=example>
738 <p>For example, suppose the following rule:
740 <pre>body { background: url("tile.png") }</pre>
742 <p>is located in a style sheet designated by the URL:</p>
744 <pre>http://www.example.org/style/basic.css</pre>
746 <p>The background of the source document's <code><body></code> will
747 be tiled with whatever image is described by the resource designated by
748 the URL:
750 <pre>http://www.example.org/style/tile.png</pre>
752 <p>The same image will be used regardless of the URL of the source
753 document containing the <code><body<</code>.
754 </div>
756 <h2 id=numeric-types><span class=secno>5. </span> Numeric Data Types</h2>
758 <h3 id=integers><span class=secno>5.1. </span> Integers: the ‘<a
759 href="#integer-value"><code class=css><integer></code></a>’
760 type</h3>
762 <p>Integer values are denoted by <dfn
763 id=integer-value><code><integer></code></dfn>. An <dfn
764 id=integer>integer</dfn> is one or more decimal digits ‘<code
765 class=css>0</code>’ through ‘<code class=css>9</code>’
766 and corresponds to a subset of the <a
767 href="#number"><code>NUMBER</code></a> token in the <a
768 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">grammar</a>.
769 Integers may be immediately preceded by ‘<code
770 class=css>-</code>’ or ‘<code class=css>+</code>’ to
771 indicate the sign.
773 <p>Properties may restrict the integer value to some range. If the value is
774 outside the allowed range, the declaration is invalid and must be <a
775 href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
777 <h3 id=numbers><span class=secno>5.2. </span> Numbers: the ‘<a
778 href="#number-value"><code class=css><number></code></a>’ type</h3>
780 <p>Number values are denoted by <dfn
781 id=number-value><code><number></code></dfn>. A <dfn
782 id=number>number</dfn> is either an <a href="#integer"><i>integer</i></a>,
783 or zero or more decimal digits followed by a dot (.) followed by one or
784 more decimal digits. It corresponds to the <a
785 href="#number"><code>NUMBER</code></a> token in the <a
786 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">grammar</a>.
787 Like integers, numbers may also be immediately preceded by ‘<code
788 class=css>-</code>’ or ‘<code class=css>+</code>’ to
789 indicate the sign.
791 <p>Properties may restrict the number value to some range. If the value is
792 outside the allowed range, the declaration is invalid and must be <a
793 href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
795 <h3 id=percentages><span class=secno>5.3. </span> Percentages: the
796 ‘<a href="#percentage-value"><code
797 class=css><percentage></code></a>’ type</h3>
799 <p>A percentage value is denoted by <dfn
800 id=percentage-value><code><percentage></code></dfn>, consists of a
801 <a href="#number-value"><i><number></i></a> immediately followed by
802 a percent sign ‘<code class=css>%</code>’. It corresponds to
803 the <code>PERCENTAGE</code> token in the <a
804 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">grammar</a>.
806 <p>Percentage values are always relative to another value, for example a
807 length. Each property that allows percentages also defines the value to
808 which the percentage refers. The value may be that of another property for
809 the same element, a property for an ancestor element, or a value of the
810 formatting context (e.g., the width of a <i>containing block</i>). When a
811 percentage value is set for a property of the <i>root</i> element and the
812 percentage is defined as referring to the inherited value of some
813 property, the resultant value is the percentage times the <i>initial
814 value</i> of that property.
816 <p>Properties may restrict the percentage value to some range. If the value
817 is outside the allowed range, the declaration is invalid and must be <a
818 href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
820 <h2 id=lengths><span class=secno>6. </span> Distance Units: the ‘<a
821 href="#length-value"><code class=css><length></code></a>’ type</h2>
823 <p>Lengths refer to distance measurements and are denoted by <dfn
824 id=length-value><code><length></code></dfn> in the property
825 definitions. A length is a <a href="#dimension"><i>dimension</i></a>. A
826 zero length may be represented instead as the <a
827 href="#number-value"><code><number></code></a> ‘<code
828 class=css>0</code>’. (In other words, for zero lengths the unit
829 identifier is optional.)
831 <p> A <dfn id=dimension>dimension</dfn> is a <a
832 href="#number"><i>number</i></a> immediately followed by a unit
833 identifier. It corresponds to the <a
834 href="#dimension"><code>DIMENSION</code></a> token in the <a
835 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">grammar</a>.
836 <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> Like
837 keywords, unit identifiers are case-insensitive within the ASCII range.
839 <p>Properties may restrict the length value to some range. If the value is
840 outside the allowed range, the declaration is invalid and must be <a
841 href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
843 <p>While some properties allow negative length values, this may complicate
844 the formatting and there may be implementation-specific limits. If a
845 negative length value is allowed but cannot be supported, it must be
846 converted to the nearest value that can be supported.
848 <p>In cases where the <a href="#used-value">used</a> length cannot be
849 supported, user agents must approximate it in the <a
850 href="#actual-value">actual</a> value.
852 <p>There are two types of length units: relative and absolute.
854 <h3 id=relative-lengths><span class=secno>6.1. </span> Relative lengths</h3>
856 <p><dfn id=relative-length-units title="relative length">Relative length
857 units</dfn> specify a length relative to another length. Style sheets that
858 use relative units can more easily scale from one output environment to
859 another.
861 <p>The relative units are:
863 <table class=data>
864 <caption>Informative Summary of Relative Units</caption>
866 <thead>
867 <tr>
868 <th>unit
870 <th>relative to
872 <tbody>
873 <tr>
874 <td>‘<a href="#em-unit"><code class=css>em</code></a>’
876 <td>font size of the element
878 <tr>
879 <td>‘<a href="#ex-unit"><code class=css>ex</code></a>’
881 <td><i>x-height</i> of the element's font
883 <tr>
884 <td>‘<a href="#ch-unit"><code class=css>ch</code></a>’
886 <td>width of the "0" glyph in the element's font
888 <tr>
889 <td>‘<a href="#rem-unit"><code class=css>rem</code></a>’
891 <td>font size of the root element
893 <tr>
894 <td>‘<a href="#vw-unit"><code class=css>vw</code></a>’
896 <td>viewport's width
898 <tr>
899 <td>‘<a href="#vh-unit"><code class=css>vh</code></a>’
901 <td>viewport's height
903 <tr>
904 <td>‘<a href="#vm-unit"><code class=css>vm</code></a>’
906 <td>minimum of the viewport's height and width
907 </table>
909 <p>Child elements do not inherit the relative values as specified for their
910 parent; they inherit the <a href="#computed-value">computed values</a>.
912 <h4 id=font-relative-lengths><span class=secno>6.1.1. </span> Font-relative
913 lengths: the ‘<a href="#em-unit"><code
914 class=css>em</code></a>’, ‘<a href="#ex-unit"><code
915 class=css>ex</code></a>’, ‘<a href="#ch-unit"><code
916 class=css>ch</code></a>’, ‘<a href="#rem-unit"><code
917 class=css>rem</code></a>’ units</h4>
919 <p>Aside from ‘<a href="#rem-unit"><code
920 class=css>rem</code></a>’ (which refers to the font-size of the root
921 element), the font-relative lengths refer to the computed font metrics of
922 the element on which they are used. The exception is when they occur in
923 the value of the ‘<code class=property>font-size</code>’
924 property itself, in which case they refer to the font metrics of the
925 parent element (or the font metrics corresponding to the initial values of
926 the ‘<code class=property>font</code>’ property, if the
927 element has no parent).
929 <dl>
930 <dt><dfn id=em-unit title=em>em unit</dfn>
932 <dd>
933 <p>Equal to the computed value of the ‘<code
934 class=property>font-size</code>’ property of the element on which
935 it is used.
937 <div class=example>
938 <p>The rule:</p>
940 <pre>h1 { line-height: 1.2em }</pre>
942 <p>means that the line height of <code>h1</code> elements will be 20%
943 greater than the font size of <code>h1</code> element. On the other
944 hand:
946 <pre>h1 { font-size: 1.2em }</pre>
948 <p>means that the font size of <code>h1</code> elements will be 20%
949 greater than the font size inherited by <code>h1</code> elements.</p>
950 </div>
952 <dt><dfn id=ex-unit title=ex>ex unit</dfn>
954 <dd>
955 <p>Equal to the font's x-height. The x-height is so called because it is
956 often equal to the height of the lowercase "x". However, an ‘<a
957 href="#ex-unit"><code class=css>ex</code></a>’ is defined even for
958 fonts that do not contain an "x".
960 <p>The x-height of a font can be found in different ways. Some fonts
961 contain reliable metrics for the x-height. If reliable font metrics are
962 not available, UAs may determine the x-height from the height of a
963 lowercase glyph. One possible heuristic is to look at how far the glyph
964 for the lowercase "o" extends below the baseline, and subtract that
965 value from the top of its bounding box. In the cases where it is
966 impossible or impractical to determine the x-height, a value of 0.5em
967 must be assumed.
969 <dt><dfn id=ch-unit title=ch>ch unit</dfn>
971 <dd>
972 <p>Equal to the advance measure of the "0" (ZERO, U+0030) glyph found in
973 the font used to render it.
975 <dt><dfn id=rem-unit title=rem>rem unit</dfn>
977 <dd>
978 <p>Equal to the computed value of ‘<code
979 class=property>font-size</code>’ on the root element.
981 <p>When specified on the ‘<code
982 class=property>font-size</code>’ property of the root element, the
983 ‘<a href="#rem-unit"><code class=css>rem</code></a>’ units
984 refer to the property's <em>initial value</em>.</p>
985 </dl>
987 <h4 id=viewport-relative-lengths><span class=secno>6.1.2. </span>
988 Viewport-relative lengths: the ‘<a href="#vw-unit"><code
989 class=css>vw</code></a>’, ‘<a href="#vh-unit"><code
990 class=css>vh</code></a>’, ‘<a href="#vm-unit"><code
991 class=css>vm</code></a>’ units</h4>
993 <p>The viewport-relative lengths are relative to the size of the initial
994 containing block. When the height or width of the viewport is changed,
995 they are scaled proportionally.
997 <dl>
998 <dt><dfn id=vw-unit title=vw>vw unit</dfn>
1000 <dd>Equal to 1/100th of the width of the initial containing block.
1001 <div class=example>
1002 <p>In the example below, if the width of the viewport is 200mm, the font
1003 size of <code>h1</code> elements will be 16mm (i.e.
1004 (8×200mm)/100).
1006 <pre>h1 { font-size: 8vw }</pre>
1007 </div>
1009 <dt><dfn id=vh-unit title=vh>vh unit</dfn>
1011 <dd>Equal to 1/100th of the height of the initial containing block.
1013 <dt><dfn id=vm-unit title=vm>vm unit</dfn>
1015 <dd>Equal to the smaller of ‘<a href="#vw-unit"><code
1016 class=css>vw</code></a>’ or ‘<a href="#vh-unit"><code
1017 class=css>vh</code></a>’.
1018 <p class=issue>Do we need this now that we have the min() function?
1019 </dl>
1021 <h3 id=absolute-lengths><span class=secno>6.2. </span> Absolute lengths:
1022 the ‘<code class=css>cm</code>’, ‘<code
1023 class=css>mm</code>’, ‘<code class=css>in</code>’,
1024 ‘<code class=css>pt</code>’, ‘<code
1025 class=css>pc</code>’, ‘<code class=css>px</code>’ units</h3>
1027 <p>The <dfn id=absolute-length-units>absolute length units</dfn> are fixed
1028 in relation to each other and anchored to some physical measurement. They
1029 are mainly useful when the output environment is known. The absolute units
1030 consist of the physical units (in, cm, mm, pt, pc) and the px unit:
1032 <table class=data>
1033 <thead>
1034 <tr>
1035 <th>unit
1037 <th>definition
1039 <tbody>
1040 <tr>
1041 <td>‘<code class=css>cm</code>’
1043 <td>centimeters
1045 <tr>
1046 <td>‘<code class=css>mm</code>’
1048 <td>millimeters
1050 <tr>
1051 <td>‘<code class=css>in</code>’
1053 <td>inches; 1in is equal to 2.54cm
1055 <tr>
1056 <td>‘<code class=css>px</code>’
1058 <td>pixels; 1px is equal to 1/96th of 1in
1060 <tr>
1061 <td>‘<code class=css>pt</code>’
1063 <td>points; 1pt is equal to 1/72nd of 1in
1065 <tr>
1066 <td>‘<code class=css>pc</code>’
1068 <td>picas; 1pc is equal to 12pt
1069 </table>
1071 <pre class=example>
1072 h1 { margin: 0.5in } /* inches */
1073 h2 { line-height: 3cm } /* centimeters */
1074 h3 { word-spacing: 4mm } /* millimeters */
1075 h4 { font-size: 12pt } /* points */
1076 h4 { font-size: 1pc } /* picas */
1077 p { font-size: 12px } /* px */</pre>
1079 <p>For a CSS device, these dimensions are either anchored (i) by relating
1080 the physical units to their physical measurements, or (ii) by relating the
1081 pixel unit to the <a href="#reference-pixel"><i>reference pixel</i></a>.
1082 For print media and similar high-resolution devices, the anchor unit
1083 should be one of the standard physical units (inches, centimeters, etc).
1084 For lower-resolution devices, and devices with unusual viewing distances,
1085 it is recommended instead that the anchor unit be the pixel unit. For such
1086 devices it is recommended that the pixel unit refer to the whole number of
1087 device pixels that best approximates the reference pixel.
1089 <p class=note>Note that if the anchor unit is the pixel unit, the physical
1090 units might not match their physical measurements. Alternatively if the
1091 anchor unit is a physical unit, the pixel unit might not map to a whole
1092 number of device pixels.
1094 <p class=note>Note that this definition of the pixel unit and the physical
1095 units differs from previous versions of CSS. In particular, in previous
1096 versions of CSS the pixel unit and the physical units were not related by
1097 a fixed ratio: the physical units were always tied to their physical
1098 measurements while the pixel unit would vary to most closely match the
1099 reference pixel. (This change was made because too much existing content
1100 relies on the assumption of 96dpi, and breaking that assumption breaks the
1101 content.)
1103 <p>The <dfn id=reference-pixel>reference pixel</dfn> is the visual angle of
1104 one pixel on a device with a pixel density of 96dpi and a distance from
1105 the reader of an arm's length. For a nominal arm's length of 28 inches,
1106 the visual angle is therefore about 0.0213 degrees. For reading at arm's
1107 length, 1px thus corresponds to about 0.26 mm (1/96 inch).
1109 <p>The image below illustrates the effect of viewing distance on the size
1110 of a reference pixel: a reading distance of 71 cm (28 inches)
1111 results in a reference pixel of 0.26 mm, while a reading distance of
1112 3.5 m (12 feet) results in a reference pixel of 1.3 mm.
1114 <div class=figure>
1115 <p><img alt="This diagram illustrates how the definition of a pixel
1116 depends on the users distance from the viewing surface (paper or screen).
1117 The image depicts the user looking at two planes, one 28 inches (71 cm)
1118 from the user, the second 140 inches (3.5 m) from the user. An expanding
1119 cone is projected from the user's eye onto each plane. Where the cone
1120 strikes the first plane, the projected pixel is 0.26 mm high. Where the
1121 cone strikes the second plane, the projected pixel is 1.4 mm high."
1122 src=pixel1.png>
1124 <p class=caption>Showing that pixels must become larger if the viewing
1125 distance increases
1126 </div>
1128 <p>This second image illustrates the effect of a device's resolution on the
1129 pixel unit: an area of 1px by 1px is covered by a single dot in a
1130 low-resolution device (e.g. a typical computer display), while the same
1131 area is covered by 16 dots in a higher resolution device (such as a
1132 printer).
1134 <div class=figure>
1135 <p><img alt="This diagram illustrates the relationship between the
1136 reference pixel and device pixels (called "dots" below). The
1137 image depicts a high resolution (large dot density) laser printer output
1138 on the left and a low resolution monitor screen on the right. For the
1139 laser printer, one square reference pixel is implemented by 16 dots. For
1140 the monitor screen, one square reference pixel is implemented by a single
1141 dot." src=pixel2.png>
1143 <p class=caption>Showing that more device pixels (dots) are needed to
1144 cover a 1px by 1px area on a high-resolution device than on a low-res one
1146 </div>
1148 <h2 id=other-units><span class=secno>7. </span> Other Units</h2>
1150 <h3 id=angles><span class=secno>7.1. </span> Angles: the ‘<a
1151 href="#angle-value"><code class=css><angle></code></a>’ type
1152 and ‘<a href="#deg"><code class=css>deg</code></a>’, ‘<a
1153 href="#grad"><code class=css>grad</code></a>’, ‘<a
1154 href="#rad"><code class=css>rad</code></a>’, ‘<a
1155 href="#turn"><code class=css>turn</code></a>’ units</h3>
1157 <p>Angle values are <i>dimensions</i> denoted by <dfn
1158 id=angle-value><angle></dfn>. The angle unit identifiers are:
1160 <dl>
1161 <dt><dfn id=deg title=deg>deg</dfn>
1163 <dd>Degrees. There are 360 degrees in a full circle.
1165 <dt><dfn id=grad title=grad>grad</dfn>
1167 <dd>Gradians. There are 400 gradians in a full circle.
1169 <dt><dfn id=rad title=rad>rad</dfn>
1171 <dd>Radians. There are 2π radians in a full circle. <span
1172 class=issue>Who is going to use this anyway?</span>
1174 <dt><dfn id=turn title=turn>turn</dfn>
1176 <dd>Turns. There is 1 turn in a full circle.
1177 </dl>
1179 <p>For example, a right angle is ‘<code class=css>90deg</code>’
1180 or ‘<code class=css>100grad</code>’ or ‘<code
1181 class=css>0.25turn</code>’ or approximately ‘<code
1182 class=css>1.570796326794897rad</code>’.
1184 <h3 id=time><span class=secno>7.2. </span> Times: the ‘<a
1185 href="#time-value"><code class=css><time></code></a>’ type and
1186 ‘<a href="#s"><code class=css>s</code></a>’, ‘<a
1187 href="#ms"><code class=css>ms</code></a>’ units</h3>
1189 <p>Time values are <i>dimensions</i> denoted by <dfn
1190 id=time-value><time></dfn>. The time unit identifiers are:
1192 <dl>
1193 <dt><dfn id=s title=s>s</dfn>
1195 <dd>Seconds.
1197 <dt><dfn id=ms title=ms>ms</dfn>
1199 <dd>Milliseconds. There are 1000 milliseconds in a second.
1200 </dl>
1202 <p>Properties may restrict the time value to some range. If the value is
1203 outside the allowed range, the declaration is invalid and must be <a
1204 href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
1206 <h3 id=frequencies-the-ltfrequencygt-type-and-h><span class=secno>7.3.
1207 </span>Frequencies: the ‘<a href="#frequency-value"><code
1208 class=css><frequency></code></a>’ type and ‘<a
1209 href="#hz"><code class=css>Hz</code></a>’, ‘<a
1210 href="#khz"><code class=css>kHz</code></a>’ units</h3>
1212 <p>Frequency values are <i>dimensions</i> denoted by <dfn
1213 id=frequency-value><frequency></dfn>. The frequency unit identifiers
1214 are:
1216 <dl>
1217 <dt><dfn id=hz title=Hz>Hz</dfn>
1219 <dd>Hertz. It represents the number of occurrences per second.
1221 <dt><dfn id=khz title=kHz>kHz</dfn>
1223 <dd>KiloHertz. A kiloHertz is 1000 Hertz.
1224 <p>For example, when representing sound pitches, 200Hz (or 200hz) is a
1225 bass sound, and 6kHz (or 6khz) is a treble sound.</p>
1227 <h4 id=the-calc-min-and-max-functions><span class=secno>7.3.1. </span>The
1228 ‘<a href="#calc"><code class=property>calc</code></a>’,
1229 ‘<a href="#min"><code class=property>min</code></a>’ and
1230 ‘<a href="#max"><code class=property>max</code></a>’
1231 functions</h4>
1233 <p>The <dfn id=calc>calc()</dfn>, <dfn id=min>min()</dfn>, and <dfn
1234 id=max>max()</dfn> functions can be used wherever length, frequency,
1235 angle, time, or number values are allowed.
1237 <div class=example>
1238 <pre>
1239 section {
1240 float: left;
1241 margin: 1em; border: solid 1px;
1242 width: calc(100%/3 - 2*1em - 2*1px);
1243 }
1244 </pre>
1245 </div>
1247 <div class=example>
1248 <pre>
1249 p {
1250 margin: calc(1rem - 2px) calc(1rem - 1px);
1251 }
1252 </pre>
1253 </div>
1255 <div class=example>
1256 <pre>
1257 p { font-size: min(10px, 3em) }
1258 blockquote { font-size: max(30px, 3em) }
1259 </pre>
1260 </div>
1262 <div class=example>
1263 <pre>
1264 .box { width: min(10% + 20px, 300px) }
1265 </pre>
1266 </div>
1268 <p>The expression language of these functions is described by the grammar
1269 and prose below.
1271 <pre>
1272 S : calc | min | max;
1273 calc : "calc(" S* sum ")" S*;
1274 min : "min(" S* sum [ "," S* sum ]* ")" S*;
1275 max : "max(" S* sum [ "," S* sum ]* ")" S*;
1276 sum : product [ [ "+" | "-" ] S* product ]*;
1277 product : unit [ [ "*" | "/" | "mod" ] S* unit ]*;
1278 unit : ["+"|"-"]? [ NUMBER S* | DIMENSION S* | PERCENTAGE S* |
1279 min | max | "(" S* sum ")" S* ];
1280 </pre>
1282 <p>The context of the expression imposes a target type, which is one of
1283 length, frequency, angle, time, or number. NUMBER tokens are of type
1284 number. DIMENSION tokens have types of their units (‘<code
1285 class=property>cm</code>’ is length, ‘<a href="#deg"><code
1286 class=property>deg</code></a>’ is angle etc.); any DIMENSION whose
1287 type does not match the target type is not allowed and must be a parse
1288 error. If percentages are accepted in that context and convertible to
1289 the target type, a PERCENTAGE token in the expression has the target
1290 type; otherwise percentages are not allowed and must be a parse error.
1292 <p>To make expressions simpler, operators have restrictions on the types
1293 they accept. At each operator, the types of the left and right side have
1294 to be checked for these restrictions. If compatible, they return roughly
1295 as follows (the following ignores precedence rules on the operators for
1296 simplicity):
1298 <ol>
1299 <li>At ",", "+", "-":<br>
1300 check: both sides have the same type<br>
1301 return: that type
1303 <li>At "*":<br>
1304 check: at least one side is "number" <br>
1305 return: the type of the other side
1307 <li>At "/":<br>
1308 check: right side is "number"<br>
1309 return: the type of the left side
1310 </ol>
1312 <p>Division by zero is a parse error.
1314 <p>The value resulting from an expression must be clamped to the range
1315 allowed in the target context.
1317 <div class=example> These two are equivalentequivalent to ‘<code
1318 class=css>width: 0px</code>’ since widths smaller than 0px are not
1319 allowed.
1320 <pre>
1321 width: calc(5px - 10px);
1322 width: 0px;
1323 </pre>
1324 </div>
1326 <p>Given the complexities of ‘<code
1327 class=property>width</code>’ and ‘<code
1328 class=property>height</code>’ on table cells and table elements,
1329 calc() expressions for ‘<code class=property>width</code>’
1330 and ‘<code class=property>height</code>’ on table columns,
1331 table column groups, table rows, table row groups, and table cells in
1332 both auto and fixed layout tables are treated as if ‘<code
1333 class=property>auto</code>’ had been specified.
1335 <h3 id=ltcolorgt><span class=secno>7.4. </span><color></h3>
1337 <p><em>This section is not normative. The CSS3 Color module <a
1338 href="#CSS3COLOR" rel=biblioentry>[CSS3COLOR]<!--{{!CSS3COLOR}}--></a>
1339 defines the CSS3 color values.</em>
1341 <p>Color values are denoted by <dfn id=ltcolorgt0><color></dfn> in
1342 the value definitions.
1344 <p>A <dfn id=color>color</dfn> value can either be a keyword, a numerical
1345 specification in a functional notation, or a numerical RGB specification
1346 in a hexadecimal notation. The hexadecimal notation is special shorthand
1347 format that allows compact color descriptions.
1349 <div class=example>
1350 <pre>
1351 em { color: #F00 }
1352 span.issue { color: red }
1353 * { color: hsl(120, 75%, 75%) }
1354 </pre>
1355 </div>
1357 <h3 id=ltattrgt><span class=secno>7.5. </span><attr></h3>
1359 <p class=issue>Describe the feature fully here, not just a delta from CSS
1360 21.
1362 <p class=issue>When attr is set on a pseudo-element, it should apply to
1363 the originating element
1365 <p>In CSS2.1 <a href="#CSS21"
1366 rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>, the ‘<code
1367 class=css>attr()</code>’ expression always returns a string. In
1368 CSS3, the ‘<code class=css>attr()</code>’ expression can
1369 return many different types. The new syntax for the attr() expression
1370 is:
1372 <pre>
1373 'attr(' ident [ ',' <type> [ ',' <value> ]? ]? ')'
1374 </pre>
1376 <p>The first argument represents the attribute name. The value of the
1377 attribute with that name on the element whose computed values are being
1378 computed is used as the value of the expression, according to the rules
1379 given below.
1381 <p>The first argument accepts an optional namespace prefix to identify
1382 the namespace of the attribute. The namespace prefix and the attribute
1383 name is separated by ‘<code class=css>|</code>’, with no
1384 whitespace before or after the separator <a href="#CSS3NAMESPACE"
1385 rel=biblioentry>[CSS3NAMESPACE]<!--{{CSS3NAMESPACE}}--></a>.
1387 <p>The second argument (which is optional but must be present if the
1388 third argument is present) is a <type> and tells the UA how to
1389 interpret the attribute value. It may be one of the values from the list
1390 below.
1392 <p>The third argument (which is optional) is a CSS value which must be
1393 valid where the attr() expression is placed. If it is not valid, then
1394 the whole attr() expression is invalid.
1396 <p>If the attribute named by the first argument is missing, cannot be
1397 parsed, or is invalid for the property, then the value returned by
1398 attr() will be the third argument, or, if the third argument is absent,
1399 will be the value given as the default for the relevant type in the list
1400 below.
1402 <dl>
1403 <dt>string
1405 <dd>The attribute value will be interpreted as the contents of a CSS
1406 string. The default is the empty string.
1408 <dt>color
1410 <dd>The attribute value will be interpreted as a CSS <color> value.
1411 The default is UA dependent but must be the same as the initial value
1412 of the ‘<a href="#color"><code
1413 class=property>color</code></a>’ property.
1415 <dt>url
1417 <dd>The attribute value will be interpreted as the URI part of a
1418 ‘<a href="#url"><code class=css>url()</code></a>’
1419 expression. The default is a UA-dependent URI defined to point to a
1420 non-existent document with a generic error condition. (i.e. it
1421 shouldn't be an FTP URI that causes a DNS error, or an HTTP URI that
1422 results in a 404, it should be a nondescript error condition.)
1424 <dt>integer
1426 <dd>The attribute value will be interpreted as a CSS integer. The
1427 default is 0. The default should also be used if the property in
1428 question only accepts integers within a certain range and the attribute
1429 is out of range.
1431 <dt>number
1433 <dd>The attribute value will be interpreted as a CSS number. The default
1434 is 0.0. The default should also be used if the property in question
1435 only accepts numbers within a certain range and the attribute is out of
1436 range.
1438 <dt>length, angle, time, frequency
1440 <dd>The attribute value will be interpreted as a CSS length, angle, time
1441 or frequency (respectively), and the unit identifier (if any) will
1442 appear in the attribute value. The default is 0. The default should
1443 also be used if the property in question only accepts values within a
1444 certain range (e.g. positive lengths or angles from 0 to 90deg) and the
1445 attribute is out of range (e.g. a negative length or 180deg).
1447 <dt>em, ex, px, gr, rem, vw, vh, vm, mm, cm, in, pt, pc, deg, grad, rad,
1448 ms, s, Hz, kHz, %
1450 <dd>The attribute value will be interpreted as a float, with the given
1451 type suffixed as a unit. The default is 0 in the relevant units.
1452 </dl>
1454 <p class=issue>Should there also be a "keyword" type to, e.g., support
1455 ‘<code class=css>float: attr(align)</code>’</p>
1457 <p>If the <type> is missing, ‘<code
1458 class=property>string</code>’ is implied.
1460 <p class=issue>Ideally, it shouldn't be necessary to specify the type if
1461 it is obvious. For example, this should be valid: "<tt>background-image:
1462 attr(href);</tt>". This could be described as: <q>If the property only
1463 accepts one type of value (aside from ‘<code
1464 class=property>inherit</code>’ and ‘<code
1465 class=property>initial</code>’), that type is implied</q>.
1467 <p>The attr() form is only valid if the type given (or implied, if it is
1468 missing) is valid for the property. For example, all of the following
1469 are invalid and would cause a parse-time error (and thus cause the
1470 relevant declaration, in this case all of them, to be ignored):
1472 <div class="illegal example">
1473 <p style="display:none">Illegal Examples:
1475 <pre>
1476 content: attr(title, color); /* 'content' doesn't accept colors */
1478 content: attr(end-of-quote, string, inherit) close-quote; /* the
1479 'inherit' value is not allowed there, since the result would be
1480 'inherit close-quote', which is invalid. */
1482 margin: attr(vertical, length) attr(horizontal, deg); /* deg
1483 units are not valid at that point */
1484 <!--
1485 font: attr(weight, integer) attr(size, length)/attr(height,
1486 integer) attr(family, string); /* invalid because
1487 <'font-weight'>s are not integers, but identifiers. */
1488 -->
1489 color: attr(color); /* 'color' doesn't accept strings */
1490 </pre>
1491 </div>
1493 <p>The attr() expression cannot return everything, for example it cannot
1494 do counters, named strings, quotes, or values such as ‘<code
1495 class=property>auto</code>’, ‘<code
1496 class=property>nowrap</code>’, or ‘<code
1497 class=property>baseline</code>’. This is intentional, as the
1498 intent of the ‘<code class=css>attr()</code>’ expression is
1499 not to make it possible to describe a presentational language's
1500 formatting using CSS, but to enable CSS to take semantic data into
1501 account.
1503 <p>Note that the default value need not be of the type given. For
1504 instance, if the type required of the attribute by the author is
1505 ‘<code class=property>px</code>’, the default could still be
1506 ‘<code class=css>5em</code>’.
1508 <div class=example>
1509 <p>Examples:
1511 <pre>
1512 <stock>
1513 <wood length="12"/>
1514 <wood length="5"/>
1515 <metal length="19"/>
1516 <wood length="4"/>
1517 </stock>
1519 stock::before {
1520 display: block;
1521 content: "To scale, the lengths of materials in stock are:";
1522 }
1523 stock > * {
1524 display: block;
1525 width: attr(length, em); /* default 0 */
1526 height: 1em;
1527 border: solid thin;
1528 margin: 0.5em;
1529 }
1530 wood {
1531 background: orange url(wood.png);
1532 }
1533 metal {
1534 background: silver url(metal.png);
1535 }
1537 /* this also uses a possible extension to the 'content' property
1538 to handle replaced content and alternatives to unavailable,
1539 corrupted or unsupported content */
1540 img {
1541 content: replaced attr(src, url), attr(alt, string, none);
1542 height: attr(height, px, auto);
1543 width: attr(width, px, auto);
1544 }
1545 </pre>
1546 </div>
1548 <p>The attr() expression cannot currently fall back onto another
1549 attribute. Future versions of CSS may extend attr() in this direction.
1551 <p class=issue>Should ‘<code class=css>attr()</code>’ be
1552 allowed on any property, in any source language? For example, do we
1553 expect UAs to honor this rule for HTML documents?: <tt>P[COLOR] { color:
1554 attr(COLOR, color) }</tt>.
1556 <h3 id=ltimagegt><span class=secno>7.6. </span><image></h3>
1558 <p>TBD. <!--
1559 <h4>The 'counter' function</h4>
1561 <p><dfn title="<counter>, definition of">Counters</dfn> are denoted by
1562 identifiers (see the <span class="property">'counter-increment'</span> and
1563 <span class="property">'counter-reset'</span> properties). To refer to the
1564 value of a counter, the notation <dfn>'counter(<identifier>)'</dfn> or
1565 <dfn>'counter(<identifier>, <list-style-type>)'</dfn> is used.
1566 The default style is 'decimal'.</p>
1568 <p>To refer to a sequence of nested counters of the same name, the notation
1569 is 'counters(<identifier>, <string>)' or
1570 'counters(<identifier>, <string>, <list-style-type>)'. See
1571 "Nested counters and scope" [add ref] in the chapter on generated content
1572 [add ref].</p>
1574 <p>In CSS2.1, the values of counters can only be referred to from the <span
1575 class="property">'content'</span> property. Note that 'none' is a possible
1576 <list-style-type>: 'counter(x, none)' yields an empty string.</p>
1578 <div class="example">
1579 <p style="display:none">Example(s):</p>
1581 <p>Here is a style sheet that numbers paragraphs (P) for each chapter (H1).
1582 The paragraphs are numbered with roman numerals, followed by a period and a
1583 space:</p>
1585 <pre>
1586 p { counter-increment: par-num }
1587 h1 { counter-reset: par-num }
1588 p:before { content: counter(par-num, upper-roman) ". " }
1589 </pre>
1590 </div>
1591 -->
1594 <h3 id=ltfractiongt><span class=secno>7.7. </span><fraction></h3>
1596 <p>Some properties accept a series of length values that, in sum, should
1597 add up to a certain length. To take up any remaining space, fractions
1598 can be used.
1600 <h4 id=the-fr-unit><span class=secno>7.7.1. </span>The ‘<code
1601 class=property>fr</code>’ unit</h4>
1603 <p>The <dfn id=fr title="fr (unit)">fr</dfn> unit is used to distribute
1604 any remaining space in a series of length values. If multiple fractions
1605 are specified, they take up space proportionally to their numeric value.
1608 <div class=example>
1609 <pre>
1610 border-parts: 10px 1fr 10px;
1611 border-parts: 10px 1fr 10px 1fr 10px;
1612 border-parts: 10px 2fr 10px 2fr 10px;
1613 </pre>
1614 </div>
1616 <p>The ‘<code class=css>fr</code>’ unit can only be used in
1617 combination with regular length units.
1619 <h3 id=ltgridgt><span class=secno>7.8. </span><grid></h3>
1621 <p>A grid is a set of invisible vertical and horizontal lines that can be
1622 used to align content. In CSS3, a grid lines can be established
1623 implicitly or explicitly <a href="#CSS3COL"
1624 rel=biblioentry>[CSS3COL]<!--{{!CSS3COL}}--></a> <a href="#CSS3GRID"
1625 rel=biblioentry>[CSS3GRID]<!--{{!CSS3GRID}}--></a>. In any case, the
1626 distance between grid lines can be referred to by the ‘<code
1627 class=css>gr</code>’ unit.
1629 <h4 id=the-gr-unit><span class=secno>7.8.1. </span>The ‘<code
1630 class=property>gr</code>’ unit</h4>
1632 <p>The <dfn id=gr title="gr (unit)">gr</dfn> unit is used to position
1633 elements in relation to grid lines.
1635 <div class=example>
1636 <pre>
1637 img {
1638 float: top left multicol;
1639 float-offset: 2gr;
1640 width: 1gr }
1641 }
1642 </pre>
1643 </div>
1645 <p>Grid lines can be laid out in uneven patterns. Therefore, the
1646 ‘<code class=css>gr</code>’ unit is not linear.
1648 <div class=example>
1649 <p>For example, "2gr" is not necessarily twice as long as "1gr".
1650 </div>
1651 <!--
1653 <h3>Special cases</h3>
1655 <p>Two common types of values fall outside the types
1656 described above: the value for font families and the hexadecimal color
1657 notation.
1659 <h4>Font families</h4>
1661 <p>The <span class="property">'font'</span>
1662 and <span class="property">'font-family'</span> properties accept a
1663 comma-separated list of font families. Font families can either be the
1664 name of a certain font, or it can be one of
1665 five <em class="index">generic font families</em>: 'serif',
1666 'sans-serif', 'cursive','fantasy', and 'monospace'. Font family names
1667 are like strings, except that the quotes around them may be omitted.
1668 If quoting is omitted, any white space characters before and after the
1669 font name are ignored and any sequence of white space characters
1670 inside the font name is converted to a single space. Font family names
1671 that happen to be the same as a keyword value (e.g. 'initial',
1672 'inherit', 'default', 'serif', 'sans-serif', 'monospace', 'fantasy',
1673 and 'cursive') must be quoted to prevent confusion with the keywords
1674 with the same names. UAs must not consider these keywords as matching
1675 the ''<family-name>'' type.
1677 <p>Generic font family names are keywords and must not be quoted.
1679 <div class="example">
1680 <pre>body { font-family: "Helvetica", "Univers", "Arial", sans-serif }</pre>
1681 </div>
1682 -->
1684 <h2 id=specified-computed-used-and-actual-value><span class=secno>8.
1685 </span>Specified, computed, used, and actual values</h2>
1687 <p>The final value of a CSS3 property for a given element is the result
1688 of a four-step calculation. First, cascading and inheritance yields the
1689 <a href="#specified-value"><em>specified value</em></a> <a
1690 href="#CSS3CASCADE"
1691 rel=biblioentry>[CSS3CASCADE]<!--{{!CSS3CASCADE}}--></a>. Second,
1692 relative values are computed into absolute values as far as possible
1693 without formatting the document, thereby yielding the <a
1694 href="#computed-value"><em>computed value</em></a>. The computed value
1695 is transformed into the <a href="#used-value"><em>used value</em></a> in
1696 the formatting process. Finally, the computed value is transformed to
1697 the <a href="#actual-value"><em>actual value</em></a> based on
1698 constraints in the user agent.</p>
1700 <h3 id=finding-the-specified-value><span class=secno>8.1. </span>Finding
1701 the <dfn id=specified-value>specified value</dfn></h3>
1703 <p>The <a href="#specified-value"><em>specified value</em></a> is the
1704 output of the cascading and inheritance process <a href="#CSS3CASCADE"
1705 rel=biblioentry>[CSS3CASCADE]<!--{{!CSS3CASCADE}}--></a>.
1707 <h3 id=finding-the-computed-value><span class=secno>8.2. </span>Finding
1708 the <dfn id=computed-value>computed value</dfn></h3>
1710 <p>Specified values may be absolute (i.e., they are not specified
1711 relative to another value, as in ‘<code
1712 class=property>red</code>’ or ‘<code
1713 class=css>2mm</code>’) or relative (i.e., they are specified
1714 relative to another value, as in ‘<code
1715 class=property>auto</code>’, ‘<code
1716 class=css>2em</code>’). For absolute values, no processing is
1717 needed to find the computed value.</p>
1719 <p>For relative values, on the other hand, computation is necessary to
1720 find the computed values: percentages must be multiplied by a reference
1721 value (each property defines which value that is), values with relative
1722 units (em, ex, px) must be made absolute by multiplying with the
1723 appropriate font or pixel size, ‘<code
1724 class=property>auto</code>’ values must be computed by the
1725 formulas given with each property, certain keywords (e.g., ‘<code
1726 class=property>smaller</code>’, ‘<code
1727 class=property>bolder</code>’) must be replaced according to their
1728 definitions. See example (f), (g) and (h) in the table below.</p>
1730 <p>Also, relative URIs are computed into absolute URIs at this stage. The
1731 computed value of invalid and absolute URIs is the same as the specified
1732 value.
1734 <h3 id=finding-the-used-value><span class=secno>8.3. </span>Finding the
1735 <dfn id=used-value>used value</dfn></h3>
1737 <p>Computed values are processed as far as possible without formatting
1738 the document. Some values, however, can only be determined when the
1739 document is being laid out. For example, if the width of an element is
1740 set to be a certain percentage of its containing block, the width cannot
1741 be determined until the width of the containing block has been
1742 determined. The used value is the result of taking the computed value
1743 and resolving any remaining dependencies into an absolute value.
1745 <h3 id=finding-the-actual-value><span class=secno>8.4. </span>Finding the
1746 <dfn id=actual-value>actual value</dfn></h3>
1748 <p>A used value is in principle ready to be used, but a user agent may
1749 not be able to make use of the value in a given environment. For
1750 example, a user agent may only be able to render borders with integer
1751 pixel widths and may therefore have to approximate the computed width.
1752 Also, the font size of an element may need adjustment based on the
1753 availability of fonts or the value of the ‘<code
1754 class=property>font-size-adjust</code>’ property. The actual value
1755 is the computed value after adjustments have been made.
1757 <p>By probing the actual values of elements, much can be learned about
1758 how the document is laid out. However, not all information is recorded
1759 in the actual values. For example, the actual value of the ‘<code
1760 class=property>page-break-after</code>’ property does not reflect
1761 whether there is a page break or not after the element. Similarly, the
1762 actual value of ‘<code class=property>orphans</code>’ does
1763 not reflect how many orphan lines there is in a certain element. See
1764 examples (j) and (k) in the table below.
1766 <table>
1767 <tbody>
1768 <tr>
1769 <th>Example
1771 <th>Winning declaration
1773 <th>Property</th>
1774 <!-- <th>Cascaded value</th> -->
1776 <th>Specified value
1778 <th>Computed value
1780 <th>Used value
1782 <th>Actual value
1784 <tr>
1785 <td>a
1787 <td><tt class=declaration>text-align: left</tt>
1789 <td>text-align</td>
1790 <!-- <td>left</td>-->
1792 <td>left
1794 <td>left
1796 <td>left
1798 <td>left
1800 <tr>
1801 <td>b
1803 <td><tt class=declaration>border-width: inherit</tt>
1805 <td>border-top-width, border-right-width, border-bottom-width,
1806 border-left-width</td>
1807 <!-- <td>inherit</td> -->
1809 <td class=say>4.2px
1811 <td>4.2px
1813 <td>4.2px
1815 <td>4px
1817 <tr>
1818 <td>c
1820 <td>(no winning declaration)
1822 <td>width</td>
1823 <!-- <td>(no specified value)</td>-->
1825 <td>auto (initial value)
1827 <td>auto
1829 <td>120px
1831 <td>120px
1833 <tr>
1834 <td>d
1836 <td><tt class=declaration>list-style-position: inherit</tt>
1838 <td>list-style-position</td>
1839 <!-- <td>inherit</td> -->
1841 <td class=say>inside
1843 <td>inside
1845 <td>inside
1847 <td>inside
1849 <tr>
1850 <td>e
1852 <td><tt class=declaration>list-style-position: initial</tt>
1854 <td>list-style-position</td>
1855 <!-- <td>initial</td>-->
1857 <td>outside (initial value)
1859 <td>outside
1861 <td>outside
1863 <td>outside
1865 <tr>
1866 <td>f
1868 <td><tt class=declaration>font-size: 1.2em</tt>
1870 <td>font-size</td>
1871 <!-- <td>1.2em</td>-->
1873 <td>1.2em
1875 <td class=say>14.1px
1877 <td>14.1px
1879 <td>14px
1881 <tr>
1882 <td>g
1884 <td><tt class=declaration>width: 80%</tt>
1886 <td>width</td>
1887 <!-- <td>80%</td>-->
1889 <td>80%
1891 <td>80%
1893 <td class=say>354.2px
1895 <td>354px
1897 <tr>
1898 <td>h
1900 <td><tt class=declaration>width: auto</tt>
1902 <td>width</td>
1903 <!-- <td>auto</td>-->
1905 <td>auto
1907 <td>auto
1909 <td class=say>134px
1911 <td>134px
1913 <tr>
1914 <td>i
1916 <td><tt class=declaration>height: auto</tt>
1918 <td>height</td>
1919 <!-- <td>auto</td>-->
1921 <td>auto
1923 <td>auto
1925 <td class=say>176px
1927 <td>176px
1929 <tr>
1930 <td>j
1932 <td>(no winning declaration)
1934 <td>page-break-after</td>
1935 <!-- <td>(no specified value)</td>-->
1937 <td>auto (initial value)
1939 <td>auto
1941 <td>auto
1943 <td>auto
1945 <tr>
1946 <td>k
1948 <td><tt class=declaration>orphans: 3</tt>
1950 <td>orphans</td>
1951 <!-- <td>3</td>-->
1953 <td>3
1955 <td>3
1957 <td>3
1959 <td>3
1960 </table>
1962 <h2 class=no-num id=acknowledgments>Acknowledgments</h2>
1964 <p>Comments and suggestions from Giovanni Campagna, Christoph Päper,
1965 Keith Rarick, Alex Mogilevsky, Ian Hickson, David Baron, Edward
1966 Welbourne, Boris Zbarsky, Björn Höhrmann and Michael Day
1967 improved this module. <!--
1969 Ian's proposal:
1970 http://lists.w3.org/Archives/Member/w3c-css-wg/2002OctDec/0141.html
1971 David's proposal
1972 http://lists.w3.org/Archives/Member/w3c-css-wg/2002OctDec/0191.html
1974 -->
1977 <h2 class=no-num id=references>References</h2>
1979 <h3 class=no-num id=normative-references>Normative references</h3>
1980 <!--begin-normative--> <!-- Sorted by label -->
1981 <dl class=bibliography>
1982 <dt style="display:
1983 none"><!-- keeps the doc valid if the DL is empty --> <!---->
1985 <dt id=CSS21>[CSS21]
1987 <dd>Bert Bos; et al. <a
1988 href="http://www.w3.org/TR/2011/REC-CSS2-20110607"><cite>Cascading
1989 Style Sheets Level 2 Revision 1 (CSS 2.1)
1990 Specification.</cite></a> 7 June 2011. W3C Recommendation. URL: <a
1991 href="http://www.w3.org/TR/2011/REC-CSS2-20110607">http://www.w3.org/TR/2011/REC-CSS2-20110607</a>
1992 </dd>
1993 <!---->
1995 <dt id=CSS3CASCADE>[CSS3CASCADE]
1997 <dd>Håkon Wium Lie. <a
1998 href="http://www.w3.org/TR/2005/WD-css3-cascade-20051215"><cite>CSS3
1999 module: Cascading and inheritance.</cite></a> 15 December 2005. W3C
2000 Working Draft. (Work in progress.) URL: <a
2001 href="http://www.w3.org/TR/2005/WD-css3-cascade-20051215">http://www.w3.org/TR/2005/WD-css3-cascade-20051215</a>
2002 </dd>
2003 <!---->
2005 <dt id=CSS3COL>[CSS3COL]
2007 <dd>Håkon Wium Lie. <a
2008 href="http://www.w3.org/TR/2011/CR-css3-multicol-20110412"><cite>CSS
2009 Multi-column Layout Module.</cite></a> 12 April 2011. W3C Candidate
2010 Recommendation. (Work in progress.) URL: <a
2011 href="http://www.w3.org/TR/2011/CR-css3-multicol-20110412">http://www.w3.org/TR/2011/CR-css3-multicol-20110412</a>
2012 </dd>
2013 <!---->
2015 <dt id=CSS3COLOR>[CSS3COLOR]
2017 <dd>Tantek Çelik; Chris Lilley; L. David Baron. <a
2018 href="http://www.w3.org/TR/2011/REC-css3-color-20110607"><cite>CSS
2019 Color Module Level 3.</cite></a> 7 June 2011. W3C Recommendation. URL:
2020 <a
2021 href="http://www.w3.org/TR/2011/REC-css3-color-20110607">http://www.w3.org/TR/2011/REC-css3-color-20110607</a>
2022 </dd>
2023 <!---->
2025 <dt id=CSS3GRID>[CSS3GRID]
2027 <dd>Alex Mogilevsky; Markus Mielke. <a
2028 href="http://www.w3.org/TR/2007/WD-css3-grid-20070905"><cite>CSS Grid
2029 Positioning Module Level 3.</cite></a> 5 September 2007. W3C
2030 Working Draft. (Work in progress.) URL: <a
2031 href="http://www.w3.org/TR/2007/WD-css3-grid-20070905">http://www.w3.org/TR/2007/WD-css3-grid-20070905</a>
2032 </dd>
2033 <!---->
2034 </dl>
2035 <!--end-normative-->
2036 <h3 class=no-num id=other-references>Other references</h3>
2037 <!--begin-informative--> <!-- Sorted by label -->
2038 <dl class=bibliography>
2039 <dt style="display:
2040 none"><!-- keeps the doc valid if the DL is empty --> <!---->
2042 <dt id=CSS3CASCADE>[CSS3CASCADE]
2044 <dd>Håkon Wium Lie. <a
2045 href="http://www.w3.org/TR/2005/WD-css3-cascade-20051215"><cite>CSS3
2046 module: Cascading and inheritance.</cite></a> 15 December 2005. W3C
2047 Working Draft. (Work in progress.) URL: <a
2048 href="http://www.w3.org/TR/2005/WD-css3-cascade-20051215">http://www.w3.org/TR/2005/WD-css3-cascade-20051215</a>
2049 </dd>
2050 <!---->
2052 <dt id=CSS3NAMESPACE>[CSS3NAMESPACE]
2054 <dd>Elika J. Etemad; Anne van Kesteren. <a
2055 href="http://www.w3.org/TR/2008/CR-css3-namespace-20080523/"><cite>CSS
2056 Namespaces Module.</cite></a> 23 May 2008. W3C Candidate
2057 Recommendation. (Work in progress.) URL: <a
2058 href="http://www.w3.org/TR/2008/CR-css3-namespace-20080523/">http://www.w3.org/TR/2008/CR-css3-namespace-20080523/</a>
2059 </dd>
2060 <!---->
2062 <dt id=URI>[URI]
2064 <dd>T. Berners-Lee; R. Fielding; L. Masinter. <a
2065 href="http://www.ietf.org/rfc/rfc3986.txt"><cite>Uniform Resource
2066 Identifiers (URI): generic syntax.</cite></a> January 2005. Internet
2067 RFC 3986. URL: <a
2068 href="http://www.ietf.org/rfc/rfc3986.txt">http://www.ietf.org/rfc/rfc3986.txt</a>
2069 </dd>
2070 <!---->
2071 </dl>
2072 <!--end-informative-->
2073 <h2 class=no-num id=index>Index</h2>
2074 <!--begin-index-->
2075 <ul class=indexlist>
2076 <li>absolute length units, <a href="#absolute-length-units"
2077 title="absolute length units"><strong>6.2.</strong></a>
2079 <li>actual value, <a href="#actual-value" title="actual
2080 value"><strong>8.4.</strong></a>
2082 <li><angle>, <a href="#angle-value"
2083 title="<angle>"><strong>7.1.</strong></a>
2085 <li>calc(), <a href="#calc" title="calc()"><strong>7.3.1.</strong></a>
2087 <li>ch, <a href="#ch-unit" title=ch><strong>6.1.1.</strong></a>
2089 <li>color, <a href="#color" title=color><strong>7.4.</strong></a>
2091 <li><color>, <a href="#ltcolorgt0"
2092 title="<color>"><strong>7.4.</strong></a>
2094 <li>compound value, <a href="#compound-value" title="compound
2095 value"><strong>3.1.</strong></a>
2097 <li>computed value, <a href="#computed-value" title="computed
2098 value"><strong>8.2.</strong></a>
2100 <li>deg, <a href="#deg" title=deg><strong>7.1.</strong></a>
2102 <li>dimension, <a href="#dimension"
2103 title=dimension><strong>6.</strong></a>
2105 <li>em, <a href="#em-unit" title=em><strong>6.1.1.</strong></a>
2107 <li>ex, <a href="#ex-unit" title=ex><strong>6.1.1.</strong></a>
2109 <li><frequency>, <a href="#frequency-value"
2110 title="<frequency>"><strong>7.3.</strong></a>
2112 <li>fr (unit), <a href="#fr" title="fr
2113 (unit)"><strong>7.7.1.</strong></a>
2115 <li>functional notation, <a href="#functional-notation0"
2116 title="functional notation"><strong>3.1.</strong></a>
2118 <li>grad, <a href="#grad" title=grad><strong>7.1.</strong></a>
2120 <li>gr (unit), <a href="#gr" title="gr
2121 (unit)"><strong>7.8.1.</strong></a>
2123 <li>Hz, <a href="#hz" title=Hz><strong>7.3.</strong></a>
2125 <li>identifier, <a href="#identifier"
2126 title=identifier><strong>4.</strong></a>
2128 <li><a href="#identifier-value"><code><identifier></code></a>, <a
2129 href="#identifier-value"
2130 title="<identifier>"><strong>4.2.</strong></a>
2132 <li>‘<code class=css>inherit</code>’, <a href="#inherit"
2133 title="''inherit''"><strong>4.1.1.</strong></a>
2135 <li>‘<code class=css>initial</code>’, <a href="#initial"
2136 title="''initial''"><strong>4.1.1.</strong></a>
2138 <li>integer, <a href="#integer" title=integer><strong>5.1.</strong></a>
2140 <li><a href="#integer-value"><code><integer></code></a>, <a
2141 href="#integer-value" title="<integer>"><strong>5.1.</strong></a>
2144 <li>kHz, <a href="#khz" title=kHz><strong>7.3.</strong></a>
2146 <li><a href="#length-value"><code><length></code></a>, <a
2147 href="#length-value" title="<length>"><strong>6.</strong></a>
2149 <li>max(), <a href="#max" title="max()"><strong>7.3.1.</strong></a>
2151 <li>min(), <a href="#min" title="min()"><strong>7.3.1.</strong></a>
2153 <li>ms, <a href="#ms" title=ms><strong>7.2.</strong></a>
2155 <li>number, <a href="#number" title=number><strong>5.2.</strong></a>
2157 <li><a href="#number-value"><code><number></code></a>, <a
2158 href="#number-value" title="<number>"><strong>5.2.</strong></a>
2160 <li><a href="#percentage-value"><code><percentage></code></a>, <a
2161 href="#percentage-value"
2162 title="<percentage>"><strong>5.3.</strong></a>
2164 <li>rad, <a href="#rad" title=rad><strong>7.1.</strong></a>
2166 <li>reference pixel, <a href="#reference-pixel" title="reference
2167 pixel"><strong>6.2.</strong></a>
2169 <li>relative length, <a href="#relative-length-units" title="relative
2170 length"><strong>6.1.</strong></a>
2172 <li>rem, <a href="#rem-unit" title=rem><strong>6.1.1.</strong></a>
2174 <li>s, <a href="#s" title=s><strong>7.2.</strong></a>
2176 <li>simple value, <a href="#simple-value" title="simple
2177 value"><strong>3.1.</strong></a>
2179 <li>specified value, <a href="#specified-value" title="specified
2180 value"><strong>8.1.</strong></a>
2182 <li><a href="#string-value"><code><string></code></a>, <a
2183 href="#string-value" title="<string>"><strong>4.3.</strong></a>
2185 <li><time>, <a href="#time-value"
2186 title="<time>"><strong>7.2.</strong></a>
2188 <li>turn, <a href="#turn" title=turn><strong>7.1.</strong></a>
2190 <li>URL, <a href="#url" title=URL><strong>4.4.</strong></a>
2192 <li><a href="#url-value"><code><url></code></a>, <a
2193 href="#url-value" title="<url>"><strong>4.4.</strong></a>
2195 <li>used value, <a href="#used-value" title="used
2196 value"><strong>8.3.</strong></a>
2198 <li>vh, <a href="#vh-unit" title=vh><strong>6.1.2.</strong></a>
2200 <li>vm, <a href="#vm-unit" title=vm><strong>6.1.2.</strong></a>
2202 <li>vw, <a href="#vw-unit" title=vw><strong>6.1.2.</strong></a>
2203 </ul>
2204 <!--end-index-->
2205 </dl>
