changeset
[css-syntax] Initial draft of the CSS Stylesheets section.
Tue, 23 Jul 2013 15:04:44 +0100
- author
- Simon Sapin <simon.sapin@exyr.org>
- date
- Tue, 23 Jul 2013 15:04:44 +0100
- changeset 8741
- 0ea487450d92
- parent 8740
- 18aec6520bfb
- child 8742
- 1fe4493083f9
[css-syntax] Initial draft of the CSS Stylesheets section.
| css-syntax/Overview.html | file | annotate | diff | comparison | revisions | |
| css-syntax/Overview.src.html | file | annotate | diff | comparison | revisions |
1.1 --- a/css-syntax/Overview.html Tue Jul 23 11:34:50 2013 +0100 1.2 +++ b/css-syntax/Overview.html Tue Jul 23 15:04:44 2013 +0100 1.3 @@ -115,8 +115,8 @@ 1.4 Informal Syntax Description</a><li><a href=#the-anb-type><span class=secno>6.2</span> 1.5 The <code><an+b></code> type</a></ul><li><a href=#rule-defs><span class=secno>7</span> 1.6 Defining Grammars for Rules and Other Values</a><ul class=toc><li><a href=#declaration-rule-list><span class=secno>7.1</span> 1.7 -Defining Block Contents: the <var><declaration-list></var>, <var><rule-list></var>, and <var><stylesheet></var> productions</a></ul><li><a href=#serialization><span class=secno>8</span>Serialization</a><ul class=toc><li><a href=#serializing-anb><span class=secno>8.1</span> 1.8 -Serializing <var><an+b></var></a></ul><li><a href=#changes><span class=secno>9</span>Changes from CSS 2.1 and Selectors Level 3</a><li><a href=#acknowledgments><span class=secno></span> 1.9 +Defining Block Contents: the <var><declaration-list></var>, <var><rule-list></var>, and <var><stylesheet></var> productions</a></ul><li><a href=#css-stylesheets><span class=secno>8</span>CSS stylesheets</a><ul class=toc><li><a href=#style-rules><span class=secno>8.1</span>Style rules</a><li><a href=#charset-rules><span class=secno>8.2</span><span class=css data-autolink=maybe>@charset</span> rules</a><li><a href=#other-at-rules-rules><span class=secno>8.3</span>Other at-rules rules</a></ul><li><a href=#serialization><span class=secno>9</span>Serialization</a><ul class=toc><li><a href=#serializing-anb><span class=secno>9.1</span> 1.10 +Serializing <var><an+b></var></a></ul><li><a href=#changes><span class=secno>10</span>Changes from CSS 2.1 and Selectors Level 3</a><li><a href=#acknowledgments><span class=secno></span> 1.11 Acknowledgments</a><li><a href=#conformance><span class=secno></span> 1.12 Conformance</a><ul class=toc><li><a href=#conventions><span class=secno></span> 1.13 Document conventions</a><li><a href=#conformance-classes><span class=secno></span> 1.14 @@ -2688,9 +2688,108 @@ 1.15 </div> 1.16 1.17 1.18 - 1.19 - 1.20 -<h2 data-level=8 id=serialization><span class=secno>8 </span><span class=content>Serialization</span><a class=section-link href=#serialization>§</a></h2> 1.21 +<h2 data-level=8 id=css-stylesheets><span class=secno>8 </span><span class=content>CSS stylesheets</span><a class=section-link href=#css-stylesheets>§</a></h2> 1.22 + 1.23 +<p> A CSS stylesheet is parsed with <a href=#parse-a-stylesheet0>Parse a stylesheet</a>, 1.24 + interpreting the resulting <a href=#qualified-rule>qualified rules</a> and <a href=#at-rule>at-rules</a> as follows. 1.25 + Each of these is either transformed into a <a href=#style-rules0>style rule</a> or another type of rule, 1.26 + or is found invalid. Invalid rules are ignored with a <a href=#parse-errors>parse errors</a>. 1.27 + 1.28 + 1.29 +<h3 data-level=8.1 id=style-rules><span class=secno>8.1 </span><span class=content>Style rules</span><a class=section-link href=#style-rules>§</a></h3> 1.30 + 1.31 + <p> 1.32 + <dfn data-dfn-type=link id=style-rules0 title="style rule|style rules">Style rules</dfn> are <a href=#qualified-rule>qualified rules</a> 1.33 + that associate a <a href=http://dev.w3.org/csswg/selectors4/#selector-list>selector list</a> <a data-autolink=biblio data-biblio-type=normative href=#select title=SELECT>[SELECT]</a> 1.34 + with a list of property declarations. 1.35 + They are also called 1.36 + <a href=http://www.w3.org/TR/CSS21/syndata.html#rule-sets>rule sets</a> in <a data-autolink=biblio data-biblio-type=normative href=#css21 title=CSS21>[CSS21]</a>. 1.37 + CSS Cascading and Inheritance <a data-autolink=biblio data-biblio-type=normative href=#css3cascade title=CSS3CASCADE>[CSS3CASCADE]</a> defines how style rules participate in the cascade. 1.38 + 1.39 + <p> 1.40 + The prelude of the qualified rule is parsed as a 1.41 + <a href=http://dev.w3.org/csswg/selectors4/#selector-list>selector list</a>. 1.42 + A style rule with an invalid selector is invalid: the whole rule is ignored. 1.43 + 1.44 + <p> 1.45 + The content of the qualified rule’s block is parsed as a 1.46 + <a href=#parse-a-list-of-declarations0 title="parse a list of declarations">list of declarations</a>. 1.47 + Unless defined otherwise by another specification or a future level of this specification, 1.48 + at-rules in that list are invalid. 1.49 + Declaration for an unknown CSS property 1.50 + or whose value does not match the syntax defined by the property are invalid. 1.51 + Invalid declarations or at-rules are ignored with a <a href=#parse-errors>parse error</a>, 1.52 + they do not make the rule invalid. 1.53 + Unless otherwise specified, property names are <a href=#ascii-case-insensitive>ASCII case-insensitive</a>. 1.54 + 1.55 + <p class=note> 1.56 + The name of Custom Properties <a data-autolink=biblio data-biblio-type=informative href=#css-variables title=CSS-VARIABLES>[CSS-VARIABLES]</a> is case-sensitive. 1.57 + 1.58 + <p> 1.59 + <a href=#qualified-rule>Qualified rules</a> at the top-level of a CSS stylesheet are style rules. 1.60 + Qualified rules in other contexts may or may not be style rules, 1.61 + as defined by the context. 1.62 + 1.63 + <p class=note> 1.64 + For example qualified rules inside <span class=css data-autolink=maybe>@media</span> rules <a data-autolink=biblio data-biblio-type=informative href=#css3-conditional title=CSS3-CONDITIONAL>[CSS3-CONDITIONAL]</a> are style rules, 1.65 + but not they’re not inside <span class=css data-autolink=maybe>@keyframes</span> rules <a data-autolink=biblio data-biblio-type=informative href=#css3-animations title=CSS3-ANIMATIONS>[CSS3-ANIMATIONS]</a>. 1.66 + 1.67 + 1.68 +<h3 data-level=8.2 id=charset-rules><span class=secno>8.2 </span><span class=content><span class=css data-autolink=maybe>@charset</span> rules</span><a class=section-link href=#charset-rules>§</a></h3> 1.69 + 1.70 + <p> 1.71 + <dfn data-dfn-type=at-rule id=charset-rules0><span class=css data-autolink=maybe>@charset</span> rules</dfn> are <a href=#at-rule>at-rules</a> whose name is an <a href=#ascii-case-insensitive>ASCII case-insensitive</a> match for "charset". 1.72 + 1.73 + <p> 1.74 + An <span class=css data-autolink=maybe>@charset</span> rule is invalid if it is not at the top-level of a stylesheet, 1.75 + if it is not the very first rule of a stylesheet, 1.76 + or if does not match the following <a href=#rule-defs>grammar</a>: 1.77 + 1.78 +<pre><at-charset-rule> = @charset 〈string〉;</pre> 1.79 + <p> 1.80 + <span class=css data-autolink=maybe>@charset</span> rules have an <dfn data-dfn-type=link id=at-charset-encoding>encoding</dfn>, 1.81 + given by the value of the 〈string〉 token. 1.82 + 1.83 + <div class=issue> 1.84 + <p> 1.85 + Although I don’t think it make sense, 1.86 + current implementations seem to consider "valid" (and reflect in <a data-autolink=biblio data-biblio-type=informative href=#cssom title=CSSOM>[CSSOM]</a>) 1.87 + <span class=css data-autolink=maybe>@charset</span> rules that: 1.88 + 1.89 +<p> <ul> 1.90 + <li> 1.91 + Don’t match the byte pattern that 1.92 + <a href=#the-input-byte-stream>The input byte stream</a> looks for, 1.93 + <li> 1.94 + or contain an invalid encoding name, 1.95 + <li> 1.96 + or are in a stylesheet that was not decoded from bytes. 1.97 + (e.g. HTML <code>style</code> element.) 1.98 + </ul> 1.99 + </div> 1.100 + 1.101 + <p class=note> 1.102 + <span class=css data-autolink=maybe>@charset</span> rules may help 1.103 + <a href=#the-input-byte-stream>determine the character encoding</a> 1.104 + of a stylesheet parse from bytes, 1.105 + but they don’t have any other effect. 1.106 + 1.107 +<h3 data-level=8.3 id=other-at-rules-rules><span class=secno>8.3 </span><span class=content>Other at-rules rules</span><a class=section-link href=#other-at-rules-rules>§</a></h3> 1.108 + 1.109 + <p> 1.110 + Other specifications may define specific types of at-rules based on their name. 1.111 + Such definitions must include what contexts a given type of at-rule is valid in. 1.112 + At-rules of unknown type are invalid. 1.113 + 1.114 + <p class=example> 1.115 + <span class=css data-autolink=maybe>@import</span> rules <a data-autolink=biblio data-biblio-type=informative href=#css3cascade title=CSS3CASCADE>[CSS3CASCADE]</a> must be at the top-level of a stylesheet, 1.116 + after <span class=css data-autolink=maybe>@charset</span> rules, and before any other rules. 1.117 + 1.118 + <p class=example> 1.119 + Margin rules <a data-autolink=biblio data-biblio-type=informative href=#css3page title=CSS3PAGE>[CSS3PAGE]</a> must be directly inside a <span class=css data-autolink=maybe>@page</span> rule. 1.120 + 1.121 + 1.122 +<h2 data-level=9 id=serialization><span class=secno>9 </span><span class=content>Serialization</span><a class=section-link href=#serialization>§</a></h2> 1.123 1.124 <p> This specification does not define how to serialize CSS in general, 1.125 leaving that task to the CSSOM and individual feature specifications. 1.126 @@ -2737,7 +2836,7 @@ 1.127 so the above rule reinserts the minimum number of comments into the serialized text to ensure an accurate round-trip. 1.128 (Roughly. The 〈delim〉 rules are slightly too powerful, for simplicity.) 1.129 1.130 -<h3 data-level=8.1 id=serializing-anb><span class=secno>8.1 </span><span class=content> 1.131 +<h3 data-level=9.1 id=serializing-anb><span class=secno>9.1 </span><span class=content> 1.132 Serializing <var><an+b></var></span><a class=section-link href=#serializing-anb>§</a></h3> 1.133 1.134 <p> To serialize an <var><an+b></var> value, 1.135 @@ -2768,7 +2867,7 @@ 1.136 1.137 <p> Return <var>s</var>. 1.138 1.139 -<h2 data-level=9 id=changes><span class=secno>9 </span><span class=content>Changes from CSS 2.1 and Selectors Level 3</span><a class=section-link href=#changes>§</a></h2> 1.140 +<h2 data-level=10 id=changes><span class=secno>10 </span><span class=content>Changes from CSS 2.1 and Selectors Level 3</span><a class=section-link href=#changes>§</a></h2> 1.141 1.142 <p> <em>This section is non-normative.</em> 1.143 1.144 @@ -3047,11 +3146,11 @@ 1.145 1.146 <h3 class="no-num no-ref" id=normative><span class=content> 1.147 Normative References</span><a class=section-link href=#normative>§</a></h3> 1.148 -<div data-fill-with=normative-references><dl><dt id=rfc2119 title=RFC2119>[RFC2119]<dd>S. Bradner. <a href=http://www.ietf.org/rfc/rfc2119.txt>Key words for use in RFCs to Indicate Requirement Levels</a>. URL: <a href=http://www.ietf.org/rfc/rfc2119.txt>http://www.ietf.org/rfc/rfc2119.txt</a></dl></div> 1.149 +<div data-fill-with=normative-references><dl><dt id=css21 title=CSS21>[CSS21]<dd>Bert Bos; et al. <a href=http://www.w3.org/TR/2011/REC-CSS2-20110607/>Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification</a>. 7 June 2011. W3C Recommendation. URL: <a href=http://www.w3.org/TR/2011/REC-CSS2-20110607/>http://www.w3.org/TR/2011/REC-CSS2-20110607/</a><dt id=css3cascade title=CSS3CASCADE>[CSS3CASCADE]<dd>Håkon Wium Lie; Elika J. Etemad; Tab Atkins Jr.. <a href=http://www.w3.org/TR/2013/WD-css3-cascade-20130103/>CSS Cascading and Inheritance Level 3</a>. 3 January 2013. W3C Working Draft. (Work in progress.) URL: <a href=http://www.w3.org/TR/2013/WD-css3-cascade-20130103/>http://www.w3.org/TR/2013/WD-css3-cascade-20130103/</a><dt id=rfc2119 title=RFC2119>[RFC2119]<dd>S. Bradner. <a href=http://www.ietf.org/rfc/rfc2119.txt>Key words for use in RFCs to Indicate Requirement Levels</a>. URL: <a href=http://www.ietf.org/rfc/rfc2119.txt>http://www.ietf.org/rfc/rfc2119.txt</a><dt id=select title=SELECT>[SELECT]<dd>Tantek Çelik; et al. <a href=http://www.w3.org/TR/2011/REC-css3-selectors-20110929/>Selectors Level 3</a>. 29 September 2011. W3C Recommendation. URL: <a href=http://www.w3.org/TR/2011/REC-css3-selectors-20110929/>http://www.w3.org/TR/2011/REC-css3-selectors-20110929/</a></dl></div> 1.150 1.151 <h3 class="no-num no-ref" id=informative><span class=content> 1.152 Informative References</span><a class=section-link href=#informative>§</a></h3> 1.153 -<div data-fill-with=informative-references><dl><dt id=css3-conditional title=CSS3-CONDITIONAL>[CSS3-CONDITIONAL]<dd>L. David Baron. <a href=http://www.w3.org/TR/2012/WD-css3-conditional-20121213/>CSS Conditional Rules Module Level 3</a>. 13 December 2012. W3C Working Draft. (Work in progress.) URL: <a href=http://www.w3.org/TR/2012/WD-css3-conditional-20121213/>http://www.w3.org/TR/2012/WD-css3-conditional-20121213/</a><dt id=mediaq title=MEDIAQ>[MEDIAQ]<dd>Florian Rivoal. <a href=http://www.w3.org/TR/2012/REC-css3-mediaqueries-20120619/>Media Queries</a>. 19 June 2012. W3C Recommendation. URL: <a href=http://www.w3.org/TR/2012/REC-css3-mediaqueries-20120619/>http://www.w3.org/TR/2012/REC-css3-mediaqueries-20120619/</a><dt id=select title=SELECT>[SELECT]<dd>Tantek Çelik; et al. <a href=http://www.w3.org/TR/2011/REC-css3-selectors-20110929/>Selectors Level 3</a>. 29 September 2011. W3C Recommendation. URL: <a href=http://www.w3.org/TR/2011/REC-css3-selectors-20110929/>http://www.w3.org/TR/2011/REC-css3-selectors-20110929/</a></dl></div> 1.154 +<div data-fill-with=informative-references><dl><dt id=css-variables title=CSS-VARIABLES>[CSS-VARIABLES]<dd>Luke Macpherson; Tab Atkins Jr.; Daniel Glazman. <a href=http://www.w3.org/TR/2012/WD-css-variables-20120410/>CSS Variables Module Level 1</a>. 10 April 2012. W3C Working Draft. (Work in progress.) URL: <a href=http://www.w3.org/TR/2012/WD-css-variables-20120410/>http://www.w3.org/TR/2012/WD-css-variables-20120410/</a><dt id=css3-animations title=CSS3-ANIMATIONS>[CSS3-ANIMATIONS]<dd>Dean Jackson; et al. <a href=http://www.w3.org/TR/2012/WD-css3-animations-20120403/>CSS Animations</a>. 3 April 2012. W3C Working Draft. (Work in progress.) URL: <a href=http://www.w3.org/TR/2012/WD-css3-animations-20120403/>http://www.w3.org/TR/2012/WD-css3-animations-20120403/</a><dt id=css3-conditional title=CSS3-CONDITIONAL>[CSS3-CONDITIONAL]<dd>L. David Baron. <a href=http://www.w3.org/TR/2012/WD-css3-conditional-20121213/>CSS Conditional Rules Module Level 3</a>. 13 December 2012. W3C Working Draft. (Work in progress.) URL: <a href=http://www.w3.org/TR/2012/WD-css3-conditional-20121213/>http://www.w3.org/TR/2012/WD-css3-conditional-20121213/</a><dt id=css3page title=CSS3PAGE>[CSS3PAGE]<dd>Håkon Wium Lie; Melinda Grant. <a href=http://www.w3.org/TR/2006/WD-css3-page-20061010>CSS3 Module: Paged Media</a>. 10 October 2006. W3C Working Draft. (Work in progress.) URL: <a href=http://www.w3.org/TR/2006/WD-css3-page-20061010>http://www.w3.org/TR/2006/WD-css3-page-20061010</a><dt id=cssom title=CSSOM>[CSSOM]<dd>Anne van Kesteren. <a href=http://www.w3.org/TR/2011/WD-cssom-20110712/>CSSOM</a>. 12 July 2011. W3C Working Draft. (Work in progress.) URL: <a href=http://www.w3.org/TR/2011/WD-cssom-20110712/>http://www.w3.org/TR/2011/WD-cssom-20110712/</a><dt id=mediaq title=MEDIAQ>[MEDIAQ]<dd>Florian Rivoal. <a href=http://www.w3.org/TR/2012/REC-css3-mediaqueries-20120619/>Media Queries</a>. 19 June 2012. W3C Recommendation. URL: <a href=http://www.w3.org/TR/2012/REC-css3-mediaqueries-20120619/>http://www.w3.org/TR/2012/REC-css3-mediaqueries-20120619/</a></dl></div> 1.155 1.156 <h2 class="no-num no-ref" id=index><span class=content> 1.157 Index</span><a class=section-link href=#index>§</a></h2> 1.158 @@ -3063,6 +3162,7 @@ 1.159 <li>ASCII case-insensitive, <a href=#ascii-case-insensitive title="section 5.2">5.2</a> 1.160 <li>at-rule, <a href=#at-rule title="section 5">5</a> 1.161 <li>B, <a href=#b title="section 6">6</a> 1.162 +<li>@charset rules, <a href=#charset-rules0 title="section 8.2">8.2</a> 1.163 <li>check if three characters would start an identifier, <a href=#check-if-three-characters-would-start-an-identifier0 title="section 4.3.9">4.3.9</a> 1.164 <li>check if three characters would start a number, <a href=#check-if-three-characters-would-start-a-number0 title="section 4.3.10">4.3.10</a> 1.165 <li>check if two characters are a valid escape, <a href=#check-if-two-characters-are-a-valid-escape0 title="section 4.3.8">4.3.8</a> 1.166 @@ -3094,6 +3194,7 @@ 1.167 <li><declaration-list>, <a href=#declaration-list title="section 7.1">7.1</a> 1.168 <li>decode, <a href=#decode title="section 3.2">3.2</a> 1.169 <li>digit, <a href=#digit title="section 4.2">4.2</a> 1.170 +<li>encoding, <a href=#at-charset-encoding title="section 8.2">8.2</a> 1.171 <li>ending token, <a href=#ending-token title="section 5.4.7">5.4.7</a> 1.172 <li>end of the range, <a href=#end-of-the-range title="section 4.3.15">4.3.15</a> 1.173 <li>〈EOF〉, <a href=#eof title="section 5.2">5.2</a> 1.174 @@ -3138,6 +3239,8 @@ 1.175 <li>starts with a valid escape, <a href=#check-if-two-characters-are-a-valid-escape0 title="section 4.3.8">4.3.8</a> 1.176 <li>start with an identifier, <a href=#check-if-three-characters-would-start-an-identifier0 title="section 4.3.9">4.3.9</a> 1.177 <li>start with a number, <a href=#check-if-three-characters-would-start-a-number0 title="section 4.3.10">4.3.10</a> 1.178 +<li>style rule, <a href=#style-rules0 title="section 8.1">8.1</a> 1.179 +<li>style rules, <a href=#style-rules0 title="section 8.1">8.1</a> 1.180 <li><stylesheet>, <a href=#stylesheet title="section 7.1">7.1</a> 1.181 <li>top-level flag, <a href=#top-level-flag title="section 5.4.1">5.4.1</a> 1.182 <li>uppercase letter, <a href=#uppercase-letter title="section 4.2">4.2</a>
2.1 --- a/css-syntax/Overview.src.html Tue Jul 23 11:34:50 2013 +0100 2.2 +++ b/css-syntax/Overview.src.html Tue Jul 23 15:04:44 2013 +0100 2.3 @@ -2579,6 +2579,106 @@ 2.4 </div> 2.5 2.6 2.7 +<h2>CSS stylesheets</h2> 2.8 + 2.9 + A CSS stylesheet is parsed with <i>Parse a stylesheet</i>, 2.10 + interpreting the resulting <i>qualified rules</i> and <i>at-rules</i> as follows. 2.11 + Each of these is either transformed into a <i>style rule</i> or another type of rule, 2.12 + or is found invalid. Invalid rules are ignored with a <i>parse errors</i>. 2.13 + 2.14 + 2.15 +<h3>Style rules</h3> 2.16 + 2.17 + <p> 2.18 + <dfn title="style rule|style rules">Style rules</dfn> are <i>qualified rules</i> 2.19 + that associate a <a href="http://dev.w3.org/csswg/selectors4/#selector-list">selector list</a> [[!SELECT]] 2.20 + with a list of property declarations. 2.21 + They are also called 2.22 + <a href="http://www.w3.org/TR/CSS21/syndata.html#rule-sets">rule sets</a> in [[!CSS21]]. 2.23 + CSS Cascading and Inheritance [[!CSS3CASCADE]] defines how style rules participate in the cascade. 2.24 + 2.25 + <p> 2.26 + The prelude of the qualified rule is parsed as a 2.27 + <a href="http://dev.w3.org/csswg/selectors4/#selector-list">selector list</a>. 2.28 + A style rule with an invalid selector is invalid: the whole rule is ignored. 2.29 + 2.30 + <p> 2.31 + The content of the qualified rule’s block is parsed as a 2.32 + <i title="parse a list of declarations">list of declarations</i>. 2.33 + Unless defined otherwise by another specification or a future level of this specification, 2.34 + at-rules in that list are invalid. 2.35 + Declaration for an unknown CSS property 2.36 + or whose value does not match the syntax defined by the property are invalid. 2.37 + Invalid declarations or at-rules are ignored with a <i>parse error</i>, 2.38 + they do not make the rule invalid. 2.39 + Unless otherwise specified, property names are <i>ASCII case-insensitive</i>. 2.40 + 2.41 + <p class=note> 2.42 + The name of Custom Properties [[CSS-VARIABLES]] is case-sensitive. 2.43 + 2.44 + <p> 2.45 + <i>Qualified rules</i> at the top-level of a CSS stylesheet are style rules. 2.46 + Qualified rules in other contexts may or may not be style rules, 2.47 + as defined by the context. 2.48 + 2.49 + <p class=note> 2.50 + For example qualified rules inside ''@media'' rules [[CSS3-CONDITIONAL]] are style rules, 2.51 + but not they’re not inside ''@keyframes'' rules [[CSS3-ANIMATIONS]]. 2.52 + 2.53 + 2.54 +<h3>''@charset'' rules</h3> 2.55 + 2.56 + <p> 2.57 + <dfn>''@charset'' rules</dfn> are <i>at-rules</i> whose name is an <i>ASCII case-insensitive</i> match for "charset". 2.58 + 2.59 + <p> 2.60 + An ''@charset'' rule is invalid if it is not at the top-level of a stylesheet, 2.61 + if it is not the very first rule of a stylesheet, 2.62 + or if does not match the following <a href="#rule-defs">grammar</a>: 2.63 + 2.64 + <pre><at-charset-rule> = @charset 〈string〉;</pre> 2.65 + 2.66 + <p> 2.67 + ''@charset'' rules have an <dfn id=at-charset-encoding>encoding</dfn>, 2.68 + given by the value of the 〈string〉 token. 2.69 + 2.70 + <div class=issue> 2.71 + <p> 2.72 + Although I don’t think it make sense, 2.73 + current implementations seem to consider "valid" (and reflect in [[CSSOM]]) 2.74 + ''@charset'' rules that: 2.75 + 2.76 + <ul> 2.77 + <li> 2.78 + Don’t match the byte pattern that 2.79 + <a href="#the-input-byte-stream">The input byte stream</a> looks for, 2.80 + <li> 2.81 + or contain an invalid encoding name, 2.82 + <li> 2.83 + or are in a stylesheet that was not decoded from bytes. 2.84 + (e.g. HTML <code>style</code> element.) 2.85 + </ul> 2.86 + </div> 2.87 + 2.88 + <p class=note> 2.89 + ''@charset'' rules may help 2.90 + <a href="#the-input-byte-stream">determine the character encoding</a> 2.91 + of a stylesheet parse from bytes, 2.92 + but they don’t have any other effect. 2.93 + 2.94 +<h3>Other at-rules rules</h3> 2.95 + 2.96 + <p> 2.97 + Other specifications may define specific types of at-rules based on their name. 2.98 + Such definitions must include what contexts a given type of at-rule is valid in. 2.99 + At-rules of unknown type are invalid. 2.100 + 2.101 + <p class=example> 2.102 + ''@import'' rules [[CSS3CASCADE]] must be at the top-level of a stylesheet, 2.103 + after ''@charset'' rules, and before any other rules. 2.104 + 2.105 + <p class=example> 2.106 + Margin rules [[CSS3PAGE]] must be directly inside a ''@page'' rule. 2.107 2.108 2.109 <h2>Serialization</h2>
