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1 <html>
2 <head>
4 <script>
8 // Try to force real results
26 }
27 });
36 }
37 });
39 /* Need a better way to test this
40 test( "removeChild", function(){
41 while ( document.body.firstChild )
42 document.body.removeChild( document.body.firstChild );
43 });
44 */
48 });
51 elems = [];
55 });
62 }
63 });
68 });
73 });
76 };
77 </script>
78 </head>
79 <body>
81 <p><a href="http://www.w3.org/"><img height=48 alt=W3C src="http://www.w3.org/Icons/w3c_home" width=72></a>
87 <dl>
89 <dt>This version:
94 <dt>Latest version:
97 http://www.w3.org/TR/css3-selectors</a>
99 <dt>Previous version:
108 <dd class="vcard"><a lang="tr" class="url fn" href="http://www.tantek.com/">Tantek Çelik</a> (Invited Expert)
116 <dd class="vcard"><span class="fn">John Williams</span> (former editor, <span class="company"><a
119 </dl>
130 <a
132 <a
134 <a
136 use</a> rules apply.
140 </div>
145 tree. Selectors have been optimized for use with HTML and XML, and
146 are designed to be usable in performance-critical code.</p>
149 Style Sheets) is a language for describing the rendering of <acronym
152 screen, on paper, in speech, etc. CSS uses Selectors for binding
153 style properties to elements in the document. This document
154 describes extensions to the selectors defined in CSS level 2. These
155 extended selectors will be used by CSS level 3.
161 <p>That is, given an element and a selector, this specification
162 defines whether that element matches the selector.</p>
164 <p>These expressions can also be used, for instance, to select a set
165 of elements, or a single element from a set of elements, by
166 evaluating the expression across all the elements in a
173 <p><em>This section describes the status of this document at the
174 time of its publication. Other documents may supersede this
175 document. A list of current W3C publications and the latest revision
176 of this technical report can be found in the <a
178 http://www.w3.org/TR/.</a></em></p>
186 <p>The CSS Working Group doesn't expect that all implementations of
187 CSS3 will have to implement all selectors. Instead, there will
188 probably be a small number of variants of CSS3, called profiles. For
189 example, it may be that only a profile for interactive user agents
190 will include all of the selectors.</p>
195 document is a revision of the <a
198 implementation feedback received in the past few years. It is
199 expected that this last call will proceed straight to Proposed
200 Recommendation stage since it is believed that interoperability will
201 be demonstrable.</p>
203 <p>All persons are encouraged to review and implement this
204 specification and return comments to the (<a
206 public mailing list <a
209 Members can also send comments directly to the CSS Working
210 Group.
213 <p>This is still a draft document and may be updated, replaced, or
214 obsoleted by other documents at any time. It is inappropriate to
219 The English version of this specification is the only normative
220 version.
228 <ul>
232 </ul>
242 </ul>
244 <ul>
246 </ul>
249 <li class="tocline4"><a href="#attribute-representation">6.3.1. Representation of attributes and attributes values</a>
253 </ul>
263 <ul>
276 </ul>
278 </ul>
279 </li>
280 </ul>
282 <ul>
287 </ul>
294 <li class="tocline4"><a href="#adjacent-sibling-combinators">8.3.1. Adjacent sibling combinator</a>
295 <li class="tocline4"><a href="#general-sibling-combinators">8.3.2. General sibling combinator</a></li>
296 </ul>
297 </li>
298 </ul>
304 </ul>
311 </ul>
313 </div>
319 <p>Some features of this specification are specific to CSS, or have
320 particular limitations or rules specific to CSS. In this
321 specification, these have been described in terms of CSS2.1. <a
326 <p>All of the text of this specification is normative except
327 examples, notes, and sections explicitly marked as
328 non-normative.</p>
334 <p>The main differences between the selectors in CSS2 and those in
335 Selectors are:
337 <ul>
339 <li>the list of basic definitions (selector, group of selectors,
340 simple selector, etc.) has been changed; in particular, what was
341 referred to in CSS2 as a simple selector is now called a sequence
342 of simple selectors, and the term "simple selector" is now used for
343 the components of this sequence</li>
345 <li>an optional namespace component is now allowed in type element
346 selectors, the universal selector and attribute selectors</li>
350 <li>new simple selectors including substring matching attribute
351 selectors, and new pseudo-classes</li>
354 for pseudo-elements</li>
358 <li>profiles to be added to specifications integrating Selectors
359 and defining the set of selectors which is actually supported by
360 each specification</li>
362 <li>Selectors are now a CSS3 Module and an independent
363 specification; other specifications can now refer to this document
364 independently of CSS</li>
368 </ul>
372 <p><em>This section is non-normative, as it merely summarizes the
373 following sections.</em></p>
375 <p>A Selector represents a structure. This structure can be used as a
376 condition (e.g. in a CSS rule) that determines which elements a
377 selector matches in the document tree, or as a flat description of the
378 HTML or XML fragment corresponding to that structure.</p>
380 <p>Selectors may range from simple element names to rich contextual
381 representations.</p>
386 <thead>
387 <tr>
392 <tbody>
393 <tr>
398 selector</a></td>
400 <tr>
406 <tr>
411 selectors</a></td>
413 <tr>
419 selectors</a></td>
421 <tr>
427 selectors</a></td>
429 <tr>
435 selectors</a></td>
437 <tr>
443 selectors</a></td>
445 <tr>
451 selectors</a></td>
453 <tr>
459 selectors</a></td>
461 <tr>
466 pseudo-classes</a></td>
468 <tr>
473 pseudo-classes</a></td>
475 <tr>
478 from the last one</td>
481 pseudo-classes</a></td>
483 <tr>
488 pseudo-classes</a></td>
490 <tr>
493 from the last one</td>
496 pseudo-classes</a></td>
498 <tr>
503 pseudo-classes</a></td>
505 <tr>
510 pseudo-classes</a></td>
512 <tr>
517 pseudo-classes</a></td>
519 <tr>
524 pseudo-classes</a></td>
526 <tr>
531 pseudo-classes</a></td>
533 <tr>
538 pseudo-classes</a></td>
540 <tr>
543 nodes)</td>
546 pseudo-classes</a></td>
548 <tr>
551 which the target is not yet visited (:link) or already visited
552 (:visited)</td>
555 pseudo-classes</a></td>
557 <tr>
562 action pseudo-classes</a></td>
564 <tr>
569 pseudo-class</a></td>
571 <tr>
574 language specifies how language is determined)</td>
577 pseudo-class</a></td>
579 <tr>
582 disabled</td>
585 pseudo-classes</a></td>
587 <tr>
593 pseudo-classes</a></td>
595 <tr>
600 pseudo-element</a></td>
602 <tr>
607 pseudo-element</a></td>
609 <tr>
612 selected/highlighted by the user</td>
615 fragments pseudo-elements</a></td>
617 <tr>
622 pseudo-element</a></td>
624 <tr>
629 pseudo-element</a></td>
631 <tr>
637 selectors</a></td>
639 <tr>
644 selectors</a></td>
646 <tr>
651 pseudo-class</a></td>
653 <tr>
658 combinator</a></td>
660 <tr>
665 combinator</a></td>
667 <tr>
673 <tr>
680 <p>The meaning of each selector is derived from the table above by
682 column.</p>
686 <p>The case sensitivity of document language element names, attribute
687 names, and attribute values in selectors depends on the document
688 language. For example, in HTML, element names are case-insensitive,
689 but in XML, they are case-sensitive.</p>
702 selector or universal selector is allowed in the sequence.</p>
714 sequence of simple selectors.</p>
719 space may appear between a combinator and the simple selectors around
724 never part of white space.</p>
726 <p>The elements of a document tree that are represented by a selector
728 selector consisting of a single sequence of simple selectors
729 represents any element satisfying its requirements. Prepending another
730 sequence of simple selectors and a combinator to a sequence imposes
731 additional matching constraints, so the subjects of a selector are
732 always a subset of the elements represented by the last sequence of
733 simple selectors.</p>
735 <p>An empty selector, containing no sequence of simple selectors and
741 <p>When several selectors share the same declarations, they may be
746 <p>In this example, we condense three rules with identical
747 declarations into one. Thus,</p>
748 <pre>h1 { font-family: sans-serif }
749 h2 { font-family: sans-serif }
750 h3 { font-family: sans-serif }</pre>
753 </div>
756 because all the selectors are valid selectors. If just one of these
757 selectors were invalid, the entire group of selectors would be
758 invalid. This would invalidate the rule for all three heading
759 elements, whereas in the former case only one of the three individual
760 heading rules would be invalidated.</p>
768 element type. A type selector represents an instance of the element
769 type in the document tree.</p>
775 </div>
782 that has been previously declared may be prepended to the element name
786 <p>The namespace component may be left empty to indicate that the
787 selector is only to represent elements with no declared namespace.</p>
789 <p>An asterisk may be used for the namespace prefix, indicating that
790 the selector represents elements in any namespace (including elements
791 with no namespace).</p>
793 <p>Element type selectors that have no namespace component (no
794 namespace separator), represent elements without regard to the
795 element's namespace (equivalent to "<code>*|</code>") unless a default
796 namespace has been declared. If a default namespace has been declared,
797 the selector will represent only elements in the default
798 namespace.</p>
800 <p>A type selector containing a namespace prefix that has not been
802 The mechanism for declaring a namespace prefix is left up to the
803 language implementing Selectors. In CSS, such a mechanism is defined
804 in the General Syntax module.</p>
806 <p>In a namespace-aware client, element type selectors will only match
807 against the <a
809 of the element's <a
812 behaviors in down-level clients.</p>
816 <dl>
820 <dd>elements with name E in any namespace, including those without any
821 declared namespace</dd>
825 <dd>if no default namespace has been specified, this is equivalent to *|E.
826 Otherwise it is equivalent to ns|E where ns is the default namespace.</dd>
827 </dl>
832 <pre>@namespace foo url(http://www.example.com);
833 foo|h1 { color: blue }
834 foo|* { color: yellow }
835 |h1 { color: red }
836 *|h1 { color: green }
837 h1 { color: green }</pre>
842 <p>The second rule will match all elements in the
846 any declared namespace.</p>
849 namespace (including those without any declared namespace).</p>
851 <p>The last rule is equivalent to the fourth rule because no default
852 namespace has been defined.</p>
854 </div>
860 type. It represents any single element in the document tree in any
861 namespace (including those without any declared namespace) if no
862 default namespace has been specified. If a default namespace has been
866 <p>If the universal selector is not the only component of a sequence
871 <ul>
875 </ul>
876 </div>
880 omitted.</p>
884 <p>The universal selector allows an optional namespace component. It
885 is used as follows:</p>
887 <dl>
895 <dd>if no default namespace has been specified, this is equivalent to *|*.
896 Otherwise it is equivalent to ns|* where ns is the default namespace.</dd>
897 </dl>
899 <p>A universal selector containing a namespace prefix that has not
901 selector. The mechanism for declaring a namespace prefix is left up
902 to the language implementing Selectors. In CSS, such a mechanism is
903 defined in the General Syntax module.</p>
908 <p>Selectors allow the representation of an element's attributes. When
909 a selector is used as an expression to match against an element,
910 attribute selectors must be considered to match an element if that
911 element has an attribute that matches the attribute represented by the
912 attribute selector.</p>
915 selectors</a></h4>
919 <dl>
922 the attribute.</dd>
931 spaces).</dd>
941 </dl>
943 <p>Attribute values must be identifiers or strings. The
944 case-sensitivity of attribute names and values in selectors depends on
945 the document language.</p>
953 value:</p>
957 <p>In the following example, the selector represents a
963 <p>Multiple attribute selectors can be used to represent several
964 attributes of an element, or several conditions on the same
973 and "~=". The first selector will represent, for example, the value
993 <p>Similarly, the following selectors represents a
997 <pre>DIALOGUE[character=romeo]
998 DIALOGUE[character=juliet]</pre>
1000 </div>
1003 selectors</h4>
1005 <p>Three additional attribute selectors are provided for matching
1006 substrings in the value of an attribute:</p>
1008 <dl>
1018 </dl>
1020 <p>Attribute values must be identifiers or strings. The
1021 case-sensitivity of attribute names in selectors depends on the
1022 document language.</p>
1027 image:</p>
1035 </div>
1039 <p>Attribute selectors allow an optional namespace component to the
1040 attribute name. A namespace prefix that has been previously declared
1041 may be prepended to the attribute name separated by the namespace
1043 the Namespaces in the XML recommendation, default namespaces do not
1044 apply to attributes, therefore attribute selectors without a namespace
1045 component apply only to attributes that have no declared namespace
1046 (equivalent to "<code>|attr</code>"). An asterisk may be used for the
1047 namespace prefix indicating that the selector is to match all
1048 attribute names without regard to the attribute's namespace.
1050 <p>An attribute selector with an attribute name containing a namespace
1051 prefix that has not been previously declared is an <a
1053 a namespace prefix is left up to the language implementing Selectors.
1054 In CSS, such a mechanism is defined in the General Syntax module.
1059 [foo|att=val] { color: blue }
1060 [*|att] { color: yellow }
1061 [|att] { color: green }
1062 [att] { color: green }</pre>
1064 <p>The first rule will match only elements with the attribute
1068 <p>The second rule will match only elements with the attribute
1070 (including no declared namespace).</p>
1072 <p>The last two rules are equivalent and will match only elements
1074 declared to be in a namespace.</p>
1076 </div>
1080 <p>Attribute selectors represent explicitly set attribute values in
1081 the document tree. Default attribute values may be defined in a DTD or
1082 elsewhere, but cannot always be selected by attribute
1083 selectors. Selectors should be designed so that they work even if the
1084 default values are not included in the document tree.</p>
1093 knowledge of that namespace to treat default attribute values as if
1094 they were present in the document. (For example, an XHTML UA is not
1095 required to use its built-in knowledge of the XHTML DTD.)</p>
1098 choose to ignore external subsets.</p>
1110 <pre>EXAMPLE[notation=decimal] { /*... default property settings ...*/ }
1111 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1114 is set by default, i.e. not set explicitly. To catch all cases, the
1115 attribute selector for the default value must be dropped:</p>
1117 <pre>EXAMPLE { /*... default property settings ...*/ }
1118 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1121 more specific than the tag
1122 selector alone, the style declarations in the second rule will override
1123 those in the first for elements that have a "notation" attribute value
1124 of "octal". Care has to be taken that all property declarations that
1125 are to apply only to the default case are overridden in the non-default
1126 cases' style rules.</p>
1128 </div>
1136 the same meaning. The attribute value must immediately follow the
1139 <p>UAs may apply selectors using the period (.) notation in XML
1140 documents if the UA has namespace-specific knowledge that allows it to
1142 respective namespace. One such example of namespace-specific knowledge
1143 is the prose in the specification for a particular namespace (e.g. SVG
1154 <p>We can assign style information to all elements with
1163 <p>The following assigns style only to H1 elements with
1168 <p>Given these rules, the first H1 instance below would not have
1169 green text, while the second would:</p>
1174 </div>
1184 has been assigned a list of <a
1194 </div>
1197 power to the "class" attribute, authors could conceivably design their
1198 own "document language" based on elements with almost no associated
1199 presentation (such as DIV and SPAN in HTML) and assigning style
1200 information through the "class" attribute. Authors should avoid this
1201 practice since the structural elements of a document language often
1202 have recognized and accepted meanings and author-defined classes may
1203 not.</p>
1206 class attributes, their values must be concatenated with spaces
1207 between the values before searching for the class. As of this time the
1208 working group is not aware of any manner in which this situation can
1209 be reached, however, so this behavior is explicitly non-normative in
1210 this specification.</p>
1214 <p>Document languages may contain attributes that are declared to be
1215 of type ID. What makes attributes of type ID special is that no two
1216 such attributes can have the same value in a document, regardless of
1217 the type of the elements that carry them; whatever the document
1218 language, an ID typed attribute can be used to uniquely identify its
1219 element. In HTML all ID attributes are named "id"; XML applications
1220 may name ID attributes differently, but the same restriction
1221 applies.</p>
1223 <p>An ID-typed attribute of a document language allows authors to
1224 assign an identifier to one element instance in the document tree. W3C
1225 ID selectors represent an element instance based on its identifier. An
1228 identifier.</p>
1230 <p>Selectors does not specify how a UA knows the ID-typed attribute of
1231 an element. The UA may, e.g., read a document's DTD, have the
1232 information hard-coded or ask the user.
1239 <p>The following ID selector represents any element whose ID-typed
1242 <p>The following selector represents any element whose ID-typed
1245 </div>
1249 contains an element's IDs is contained in a DTD or a schema. When
1250 parsing XML, UAs do not always read the DTD, and thus may not know
1251 what the ID of an element is (though a UA may have namespace-specific
1252 knowledge that allows it to determine which attribute is the ID
1253 attribute for that namespace). If a style sheet designer knows or
1254 suspects that a UA may not know what the ID of an element is, he
1255 should use normal attribute selectors instead:
1259 <p>If an element has multiple ID attributes, all of them must be
1260 treated as IDs for that element for the purposes of the ID
1261 selector. Such a situation could be reached using mixtures of xml:id,
1262 DOM3 Core, XML DTDs, and namespace-specific knowledge.</p>
1266 <p>The pseudo-class concept is introduced to permit selection based on
1267 information that lies outside of the document tree or that cannot be
1268 expressed using the other simple selectors.</p>
1272 optionally by a value between parentheses.</p>
1274 <p>Pseudo-classes are allowed in all sequences of simple selectors
1275 contained in a selector. Pseudo-classes are allowed anywhere in
1276 sequences of simple selectors, after the leading type selector or
1277 universal selector (possibly omitted). Pseudo-class names are
1278 case-insensitive. Some pseudo-classes are mutually exclusive, while
1279 others can be applied simultaneously to the same
1280 element. Pseudo-classes may be dynamic, in the sense that an element
1281 may acquire or lose a pseudo-class while a user interacts with the
1282 document.</p>
1287 <p>Dynamic pseudo-classes classify elements on characteristics other
1288 than their name, attributes, or content, in principle characteristics
1289 that cannot be deduced from the document tree.</p>
1291 <p>Dynamic pseudo-classes do not appear in the document source or
1292 document tree.</p>
1297 <p>User agents commonly display unvisited links differently from
1298 previously visited ones. Selectors
1302 <ul>
1304 not yet been visited.</li>
1306 been visited by the user. </li>
1307 </ul>
1309 <p>After some amount of time, user agents may choose to return a
1310 visited link to the (unvisited) ':link' state.</p>
1318 <p>The following selector represents links carrying class
1323 </div>
1326 authors to abuse the :link and :visited pseudo-classes to determine
1327 which sites a user has visited without the user's consent.
1329 <p>UAs may therefore treat all links as unvisited links, or implement
1330 other measures to preserve the user's privacy while rendering visited
1331 and unvisited links differently.</p>
1334 :hover, :active, and :focus</a></h5>
1336 <p>Interactive user agents sometimes change the rendering in response
1337 to user actions. Selectors provides
1338 three pseudo-classes for the selection of an element the user is
1339 acting on.</p>
1341 <ul>
1344 designates an element with a pointing device, but does not activate
1345 it. For example, a visual user agent could apply this pseudo-class
1346 when the cursor (mouse pointer) hovers over a box generated by the
1347 element. User agents not that do not support <a
1349 media</a> do not have to support this pseudo-class. Some conforming
1350 user agents that support <a
1352 media</a> may not be able to support this pseudo-class (e.g., a pen
1353 device that does not detect hovering).</li>
1356 is being activated by the user. For example, between the times the
1357 user presses the mouse button and releases it.</li>
1360 has the focus (accepts keyboard or mouse events, or other forms of
1361 input). </li>
1363 </ul>
1365 <p>There may be document language or implementation specific limits on
1369 <p>These pseudo-classes are not mutually exclusive. An element may
1370 match several pseudo-classes at the same time.</p>
1372 <p>Selectors doesn't define if the parent of an element that is
1373 ':active' or ':hover' is also in that state.</p>
1377 <pre>a:link /* unvisited links */
1378 a:visited /* visited links */
1379 a:hover /* user hovers */
1380 a:active /* active links */</pre>
1382 <pre>a:focus
1383 a:focus:hover</pre>
1385 the pseudo-class :focus and in the pseudo-class :hover.</p>
1386 </div>
1389 and ':active' (or ':link' and ':active').</p>
1393 <p>Some URIs refer to a location within a resource. This kind of URI
1395 identifier (called the fragment identifier).</p>
1397 <p>URIs with fragment identifiers link to a certain element within the
1398 document, known as the target element. For instance, here is a URI
1400 document:</p>
1405 pseudo-class. If the document's URI has no fragment identifier, then
1406 the document has no target element.</p>
1413 URI.</p>
1414 </div>
1419 target element red and place an image before it, if there is one:</p>
1420 <pre>*:target { color : red }
1421 *:target::before { content : url(target.png) }</pre>
1422 </div>
1426 <p>If the document language specifies how the human language of an
1427 element is determined, it is possible to write selectors that
1428 represent an element based on its language. For example, in HTML <a
1431 element, and possibly by information from the protocol (such as HTTP
1433 there may be other document language-specific methods for determining
1434 the language.</p>
1437 is in language C. Whether an element is represented by a
1439 being either equal to, or a hyphen-separated substring of, the
1440 element's language value, in the same way as if performed by the <a
1442 selectors. The identifier C does not have to be a valid language
1443 name.</p>
1457 <p>The two following selectors represent an HTML document that is in
1458 Belgian, French, or German. The two next selectors represent
1460 or German.</p>
1461 <pre>html:lang(fr-be)
1462 html:lang(de)
1463 :lang(fr-be) > q
1465 </div>
1472 the look of user interface elements that are enabled — which the
1473 user can select or activate in some fashion (e.g. clicking on a button
1474 with a mouse). There is a need for such a pseudo-class because there
1475 is no way to programmatically specify the default appearance of say,
1477 would look like when it was disabled.</p>
1480 author to specify precisely how a disabled or inactive user interface
1481 element should look.</p>
1483 <p>Most elements will be neither enabled nor disabled. An element is
1484 enabled if the user can either activate it or transfer the focus to
1485 it. An element is disabled if it could be enabled, but the user cannot
1486 presently activate it or transfer focus to it.</p>
1491 <p>Radio and checkbox elements can be toggled by the user. Some menu
1492 items are "checked" when the user selects them. When such elements are
1496 attributes as described in <a
1501 in nature, and is altered by user action, since it can also be based
1510 <p>Radio and checkbox elements can be toggled by the user, but are
1511 sometimes in an indeterminate state, neither checked nor unchecked.
1512 This can be due to an element attribute, or DOM manipulation.</p>
1514 <p>A future version of this specification may introduce an
1516 <!--While the <code>:indeterminate</code> pseudo-class is dynamic in
1517 nature, and is altered by user action, since it can also be based on
1518 the presence of an element attribute, it applies to all media.</p>
1520 <p>Components of a radio-group initialized with no pre-selected choice
1523 </div>
1529 pseudo-classes</dfn> to permit selection based on extra information that lies in
1530 the document tree but cannot be represented by other simple selectors or
1531 combinators.
1533 <p>Note that standalone pieces of PCDATA (text nodes in the DOM) are
1534 not counted when calculating the position of an element in the list of
1535 children of its parent. When calculating the position of an element in
1536 the list of children of its parent, the index numbering starts at 1.
1542 the root of the document. In HTML 4, this is always the
1548 <p>The
1550 pseudo-class notation represents an element that has
1556 each. For example, this allows the selectors to address every other
1557 row in a table, and could be used to alternate the color
1560 integers. The index of the first child of an element is 1.
1571 tr:nth-child(odd) /* same */
1572 tr:nth-child(2n) /* represents every even row of an HTML table */
1573 tr:nth-child(even) /* same */
1575 /* Alternate paragraph colours in CSS */
1580 </div>
1585 included, so the syntax simplifies to
1593 </div>
1601 bar:nth-child(n+0) /* same */
1602 bar:nth-child(n) /* same */
1604 </div>
1613 </div>
1616 pseudo-class represents no element in the document tree.</p>
1621 tree.</p>
1626 </div>
1629 expression must be removed (it is effectively replaced by the "-"
1637 </div>
1643 pseudo-class notation represents an element that has
1649 as arguments.
1656 foo:nth-last-child(odd) /* represents all odd foo elements in their parent element,
1657 counting from the last one */</pre>
1658 </div>
1664 pseudo-class notation represents an element that has
1669 of that type after all the children of that type have been split into
1671 for the syntax of its argument. It also accepts the
1680 </div>
1686 pseudo-class notation represents an element that has
1698 following selector:</p>
1701 selector ends up being just as long:</p>
1703 </div>
1709 represents an element that is the first child of some other element.
1723 fragment:
1731 a:first-child /* Same (assuming a is not the root element) */</pre>
1732 </div>
1737 represents an element that is the last child of some other element.
1744 </div>
1749 represents an element that is the first sibling of its type in the list of
1750 children of its parent element.
1754 <p>The following selector represents a definition title
1757 its parent element.</p>
1760 elements in the following example but not for the third one:</p>
1772 </div>
1778 the last sibling of its type in the list of children of its parent
1779 element.</p>
1783 <p>The following selector represents the last data cell
1786 </div>
1790 <p>Represents an element that has a parent element and whose parent
1791 element has no other element children. Same as
1794 specificity.</p>
1798 <p>Represents an element that has a parent element and whose parent
1799 element has no other element children with the same element name. Same
1802 specificity.</p>
1808 no children at all. In terms of the DOM, only element nodes and text
1809 nodes (including CDATA nodes and entity references) whose data has a
1810 non-zero length must be considered as affecting emptiness; comments,
1811 PIs, and other nodes must not affect whether an element is considered
1812 empty or not.</p>
1819 following fragments:</p>
1823 </div>
1825 <h4><a name=content-selectors>6.6.6. Blank</a></h4> <!-- It's the Return of Appendix H!!! Run away! -->
1828 <!-- (used to be :contains()) -->
1834 selector</a> (excluding the negation pseudo-class itself and
1835 pseudo-elements) as an argument. It represents an element that is not
1836 represented by the argument.
1838 <!-- pseudo-elements are not simple selectors, so the above paragraph
1839 may be a bit confusing -->
1844 elements in an HTML document that are not disabled.</p>
1847 elements.</p>
1849 <p>The following group of selectors represents all HTML elements
1850 except links.</p>
1852 </div>
1854 <p>Default namespace declarations do not affect the argument of the
1855 negation pseudo-class unless the argument is a universal selector or a
1856 type selector.</p>
1860 <p>Assuming that the default namespace is bound to
1861 "http://example.com/", the following selector represents all
1862 elements that are not in that namespace:</p>
1864 <p>The following CSS selector matches any element being hovered,
1865 regardless of its namespace. In particular, it is not limited to
1866 only matching elements in the default namespace that are not being
1867 hovered, and elements not in the default namespace don't match the
1870 </div>
1876 specificity.</p>
1880 <p>Pseudo-elements create abstractions about the document tree beyond
1881 those specified by the document language. For instance, document
1882 languages do not offer mechanisms to access the first letter or first
1883 line of an element's content. Pseudo-elements allow designers to refer
1884 to this otherwise inaccessible information. Pseudo-elements may also
1885 provide designers a way to refer to content that does not exist in the
1888 content).</p>
1891 by the name of the pseudo-element.</p>
1894 in order to establish a discrimination between pseudo-classes and
1895 pseudo-elements. For compatibility with existing style sheets, user
1896 agents must also accept the previous one-colon notation for
1902 <p>Only one pseudo-element may appear per selector, and if present it
1903 must appear after the sequence of simple selectors that represents the
1905 future version of this specification may allow multiple
1906 pesudo-elements per selector.</span></p>
1911 of the first formatted line of an element.
1918 </div>
1921 HTML element. It does match a pseudo-element that conforming user
1922 agents will insert at the beginning of every paragraph.</p>
1924 <p>Note that the length of the first line depends on a number of
1925 factors, including the width of the page, the font size, etc. Thus,
1926 an ordinary HTML paragraph such as:</p>
1928 <pre>
1930 paragraph that will be broken into several
1931 lines. The first line will be identified
1932 by a fictional tag sequence. The other lines
1933 will be treated as ordinary lines in the
1935 </pre>
1937 <p>the lines of which happen to be broken as follows:
1939 <pre>
1940 THIS IS A SOMEWHAT LONG HTML PARAGRAPH THAT
1941 will be broken into several lines. The first
1942 line will be identified by a fictional tag
1943 sequence. The other lines will be treated as
1944 ordinary lines in the paragraph.
1945 </pre>
1949 fictional tag sequence helps to show how properties are inherited.</p>
1951 <pre>
1954 lines. The first line will be identified
1955 by a fictional tag sequence. The other lines
1956 will be treated as ordinary lines in the
1958 </pre>
1960 <p>If a pseudo-element breaks up a real element, the desired effect
1961 can often be described by a fictional tag sequence that closes and
1962 then re-opens the element. Thus, if we mark up the previous paragraph
1965 <pre>
1967 paragraph that will be broken into several
1969 by a fictional tag sequence. The other lines
1970 will be treated as ordinary lines in the
1972 </pre>
1974 <p>the user agent could simulate start and end tags for
1978 <pre>
1980 somewhat long HTML
1981 paragraph that will <b></SPAN></b></P::first-line><b><SPAN class="test"></b> be
1982 broken into several
1984 by a fictional tag sequence. The other lines
1985 will be treated as ordinary lines in the
1987 </pre>
1990 attached to a block-level element, an inline-block, a table-caption,
1991 or a table-cell.</p>
1994 element may occur inside a
1995 block-level descendant in the same flow (i.e., a block-level
1996 descendant that is not positioned and not a float). E.g., the first
2001 <p>The first line of a table-cell or inline-block cannot be the first
2012 <p>A UA should act as if the fictional start tags of the
2014 innermost enclosing block-level element. (Since CSS1 and CSS2 were
2015 silent on this case, authors should not rely on this behavior.) Here
2016 is an example. The fictional tag sequence for</p>
2018 <pre>
2023 </pre>
2027 <pre>
2029 <P><DIV::first-line><P::first-line>First paragraph</P::first-line></DIV::first-line></P>
2032 </pre>
2035 inline-level element, but with certain restrictions. In CSS, the
2037 pseudo-element: font properties, color property, background
2038 properties, 'word-spacing', 'letter-spacing', 'text-decoration',
2039 'vertical-align', 'text-transform', 'line-height'. UAs may apply other
2040 properties as well.</p>
2046 letter of the first line of a block, if it is not preceded by any
2047 other content (such as images or inline tables) on its line. The
2049 caps", which are common typographical effects. This type of initial
2050 letter is similar to an inline-level element if its 'float' property
2051 is 'none'; otherwise, it is similar to a floated element.</p>
2054 pseudo-elements: font properties, 'text-decoration', 'text-transform',
2055 'letter-spacing', 'word-spacing' (when appropriate), 'line-height',
2056 'float', 'vertical-align' (only if 'float' is 'none'), margin
2057 properties, padding properties, border properties, color property,
2058 background properties. UAs may apply other properties as well. To
2059 allow UAs to render a typographically correct drop cap or initial cap,
2060 the UA may choose a line-height, width and height based on the shape
2061 of the letter, unlike for normal elements.</p>
2065 <p>This example shows a possible rendering of an initial cap. Note
2067 pseudo-element is 1.1, but the UA in this example has computed the
2068 height of the first letter differently, so that it doesn't cause any
2069 unnecessary space between the first two lines. Also note that the
2072 <pre>
2073 p { line-height: 1.1 }
2074 p::first-letter { font-size: 3em; font-weight: normal }
2075 span { font-weight: bold }
2076 ...
2080 En dagelix geschrey de bange stad ontzet.
2081 </pre>
2084 </div>
2085 </div>
2090 <pre>
2097 P::first-letter { font-size: 200%; font-weight: bold; float: left }
2098 SPAN { text-transform: uppercase }
2106 </pre>
2111 <P><img src="first-letter.gif" alt="Image illustrating the combined effect of the ::first-letter and ::first-line pseudo-elements"></p>
2112 </div>
2117 <pre>
2121 T
2124 few words of an article in the Economist.
2126 </pre>
2129 the content (i.e., the initial character), while the ::first-line
2130 pseudo-element start tag is inserted right after the start tag of the
2131 block element.</p> </div>
2133 <p>In order to achieve traditional drop caps formatting, user agents
2134 may approximate font sizes, for example to align baselines. Also, the
2135 glyph outline may be taken into account when formatting.</p>
2139 punctuation classes), that precedes or follows the first letter should
2145 </div>
2152 block, list-item, table-cell, table-caption, and inline-block
2154 may allow this pesudo-element to apply to more element
2155 types.</span></p>
2158 such elements that contain text, or that have a descendant in the same
2159 flow that contains text. A UA should act as if the fictional start tag
2160 of the ::first-letter pseudo-element is just before the first text of
2161 the element, even if that first text is in a descendant.</p>
2165 <p>The fictional tag sequence for this HTMLfragment:
2168 <p>is:
2171 </div>
2173 <p>The first letter of a table-cell or inline-block cannot be the
2186 <p>In CSS, if an element is a list item ('display: list-item'), the
2188 principal box after the marker. UAs may ignore
2198 </div>
2200 <p>Some languages may have specific rules about how to treat certain
2201 letter combinations. In Dutch, for example, if the letter combination
2202 "ij" appears at the beginning of a word, both letters should be
2205 <p>If the letters that would form the ::first-letter are not in the
2207 may create a ::first-letter pseudo-element from one of the elements,
2208 both elements, or simply not create a pseudo-element.</p>
2210 <p>Similarly, if the first letter(s) of the block are not at the start
2211 of the line (for example due to bidirectional reordering), then the UA
2212 need not create the pseudo-element(s).
2217 how overlapping pseudo-elements may interact. The first letter of
2218 each P element will be green with a font size of '24pt'. The rest of
2219 the first formatted line will be 'blue' while the rest of the
2220 paragraph will be 'red'.</p>
2223 p::first-letter { color: green; font-size: 200% }
2224 p::first-line { color: blue }
2235 S
2238 ends up on two lines
2245 </div>
2251 of a document that has been highlighted by the user. This also
2252 applies, for example, to selected text within an editable text
2253 field. This pseudo-element should not be confused with the <code><a
2258 nature, and is altered by user action, it is reasonable to expect that
2259 when a UA re-renders to a static medium (such as a printed page, see
2261 dynamic medium (like screen), the UA may wish to transfer the current
2263 appropriate formatting and rendering take effect as well. This is not
2265 pseudo-element for static media.
2268 pseudo-elements: color, background, cursor (optional), outline
2269 (optional). The computed value of the 'background-image' property on
2276 can be used to describe generated content before or after an element's
2283 element including the inserted text.</p>
2289 <p>At times, authors may want selectors to describe an element that is
2290 the descendant of another element in the document tree (e.g., "an
2291 <code>EM</code> element that is contained within an <code>H1</code>
2292 element"). Descendant combinators express such a relationship. A
2294 separates two sequences of simple selectors. A selector of the form
2304 description of the following fragment:</p>
2311 either side of the "*" is not part of the universal selector; the
2312 whitespace is a combinator indicating that the DIV must be the
2313 ancestor of some element, and that that element must be an ancestor
2314 of the P.</p>
2315 <p>The following selector, which combines descendant combinators and
2320 </div>
2325 between two elements. A child combinator is made of the
2327 separates two sequences of simple selectors.
2335 <p>The following example combines descendant combinators and child
2336 combinators.</p>
2343 </div>
2345 <p>For information on selecting the first child of an element, please
2346 see the section on the <code><a
2348 above.</p>
2352 <p>There are two different sibling combinators: the adjacent sibling
2353 combinator and the general sibling combinator. In both cases,
2354 non-element nodes (e.g. text between elements) are ignored when
2355 considering adjacency of elements.</p>
2361 sequences of simple selectors. The elements represented by the two
2362 sequences share the same parent in the document tree and the element
2363 represented by the first sequence immediately precedes the element
2364 represented by the second one.</p>
2371 <p>The following selector is conceptually similar to the one in the
2372 previous example, except that it adds an attribute selector — it
2376 </div>
2383 simple selectors. The elements represented by the two sequences share
2384 the same parent in the document tree and the element represented by
2385 the first sequence precedes (not necessarily immediately) the element
2386 represented by the second one.</p>
2392 is a correct and valid, but partial, description of:</p>
2396 </div>
2402 <ul>
2404 <li>count the number of class selectors, attributes selectors, and pseudo-classes in the selector (= b)</li>
2407 </ul>
2410 are counted like any other, but the negation itself does not count as
2411 a pseudo-class.</p>
2413 <p>Concatenating the three numbers a-b-c (in a number system with a
2414 large base) gives the specificity.</p>
2427 </pre>
2428 </div>
2438 <p>The grammar below defines the syntax of Selectors. It is globally
2440 it directly, since it doesn't express the parsing conventions). The
2441 format of the productions is optimized for human consumption and some
2443 are used:</p>
2445 <ul>
2451 </ul>
2455 <pre>selectors_group
2456 : selector [ COMMA S* selector ]*
2457 ;
2459 selector
2460 : simple_selector_sequence [ combinator simple_selector_sequence ]*
2461 ;
2463 combinator
2464 /* combinators can be surrounded by white space */
2465 : PLUS S* | GREATER S* | TILDE S* | S+
2466 ;
2468 simple_selector_sequence
2469 : [ type_selector | universal ]
2470 [ HASH | class | attrib | pseudo | negation ]*
2471 | [ HASH | class | attrib | pseudo | negation ]+
2472 ;
2474 type_selector
2475 : [ namespace_prefix ]? element_name
2476 ;
2478 namespace_prefix
2479 : [ IDENT | '*' ]? '|'
2480 ;
2482 element_name
2483 : IDENT
2484 ;
2486 universal
2487 : [ namespace_prefix ]? '*'
2488 ;
2490 class
2491 : '.' IDENT
2492 ;
2494 attrib
2495 : '[' S* [ namespace_prefix ]? IDENT S*
2496 [ [ PREFIXMATCH |
2497 SUFFIXMATCH |
2498 SUBSTRINGMATCH |
2499 '=' |
2500 INCLUDES |
2501 DASHMATCH ] S* [ IDENT | STRING ] S*
2502 ]? ']'
2503 ;
2505 pseudo
2506 /* '::' starts a pseudo-element, ':' a pseudo-class */
2507 /* Exceptions: :first-line, :first-letter, :before and :after. */
2508 /* Note that pseudo-elements are restricted to one per selector and */
2509 /* occur only in the last simple_selector_sequence. */
2510 : ':' ':'? [ IDENT | functional_pseudo ]
2511 ;
2513 functional_pseudo
2514 : FUNCTION S* expression ')'
2515 ;
2517 expression
2518 /* In CSS3, the expressions are identifiers, strings, */
2519 /* or of the form "an+b" */
2520 : [ [ PLUS | '-' | DIMENSION | NUMBER | STRING | IDENT ] S* ]+
2521 ;
2523 negation
2524 : NOT S* negation_arg S* ')'
2525 ;
2527 negation_arg
2528 : type_selector | universal | HASH | class | attrib | pseudo
2529 ;</pre>
2536 case-insensitive.</p>
2539 number that current versions of Flex can deal with (decimal 255). They
2544 <pre>%option case-insensitive
2546 ident [-]?{nmstart}{nmchar}*
2547 name {nmchar}+
2548 nmstart [_a-z]|{nonascii}|{escape}
2551 escape {unicode}|\\[^\n\r\f0-9a-f]
2552 nmchar [_a-z0-9-]|{nonascii}|{escape}
2554 string {string1}|{string2}
2556 string2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*\'
2557 invalid {invalid1}|{invalid2}
2559 invalid2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*
2560 nl \n|\r\n|\r|\f
2561 w [ \t\r\n\f]*
2563 %%
2565 [ \t\r\n\f]+ return S;
2572 {ident} return IDENT;
2573 {string} return STRING;
2575 {num} return NUMBER;
2582 @{ident} return ATKEYWORD;
2583 {invalid} return INVALID;
2584 {num}% return PERCENTAGE;
2585 {num}{ident} return DIMENSION;
2591 U\+[0-9a-f?]{1,6}(-[0-9a-f]{1,6})? return UNICODE_RANGE;
2593 \/\*[^*]*\*+([^/*][^*]*\*+)*\/ /* ignore comments */
2595 . return *yytext;</pre>
2599 <h2><a name=downlevel>11. Namespaces and down-level clients</a></h2>
2601 <p>An important issue is the interaction of CSS selectors with XML
2602 documents in web clients that were produced prior to this
2603 document. Unfortunately, due to the fact that namespaces must be
2604 matched based on the URI which identifies the namespace, not the
2605 namespace prefix, some mechanism is required to identify namespaces in
2606 CSS by their URI as well. Without such a mechanism, it is impossible
2607 to construct a CSS style sheet which will properly match selectors in
2608 all cases against a random set of XML documents. However, given
2609 complete knowledge of the XML document to which a style sheet is to be
2610 applied, and a limited use of namespaces within the XML document, it
2611 is possible to construct a style sheet in which selectors would match
2612 elements and attributes correctly.</p>
2614 <p>It should be noted that a down-level CSS client will (if it
2615 properly conforms to CSS forward compatible parsing rules) ignore all
2616 <code>@namespace</code> at-rules, as well as all style rules that make
2617 use of namespace qualified element type or attribute selectors. The
2618 syntax of delimiting namespace prefixes in CSS was deliberately chosen
2619 so that down-level CSS clients would ignore the style rules rather
2620 than possibly match them incorrectly.</p>
2622 <p>The use of default namespaces in CSS makes it possible to write
2623 element type selectors that will function in both namespace aware CSS
2624 clients as well as down-level clients. It should be noted that
2625 down-level clients may incorrectly match selectors against XML
2626 elements in other namespaces.</p>
2628 <p>The following are scenarios and examples in which it is possible to
2629 construct style sheets which would function properly in web clients
2630 that do not implement this proposal.</p>
2632 <ol>
2633 <li>
2635 <p>The XML document does not use namespaces.</p>
2637 <ul>
2639 <li>In this case, it is obviously not necessary to declare or use
2640 namespaces in the style sheet. Standard CSS element type and
2641 attribute selectors will function adequately in a down-level
2642 client.</li>
2644 <li>In a CSS namespace aware client, the default behavior of
2645 element selectors matching without regard to namespace will
2646 function properly against all elements, since no namespaces are
2647 present. However, the use of specific element type selectors that
2649 will guarantee that selectors will match only XML elements that do
2650 not have a declared namespace. </li>
2652 </ul>
2654 </li>
2656 <li>
2658 <p>The XML document defines a single, default namespace used
2659 throughout the document. No namespace prefixes are used in element
2660 names.</p>
2662 <ul>
2664 <li>In this case, a down-level client will function as if
2665 namespaces were not used in the XML document at all. Standard CSS
2666 element type and attribute selectors will match against all
2667 elements. </li>
2669 </ul>
2671 </li>
2673 <li>
2675 <p>The XML document does <b>not</b> use a default namespace, all
2676 namespace prefixes used are known to the style sheet author, and
2677 there is a direct mapping between namespace prefixes and namespace
2678 URIs. (A given prefix may only be mapped to one namespace URI
2679 throughout the XML document; there may be multiple prefixes mapped
2680 to the same URI).</p>
2682 <ul>
2684 <li>In this case, the down-level client will view and match
2685 element type and attribute selectors based on their fully
2686 qualified name, not the local part as outlined in the <a
2689 to describe the fully qualified names, e.g.
2691 <code><html:h1></code>. Selectors using the qualified name
2692 will only match XML elements that use the same prefix. Other
2693 namespace prefixes used in the XML that are mapped to the same URI
2694 will not match as expected unless additional CSS style rules are
2695 declared for them.</li>
2697 <li>Note that selectors declared in this fashion will
2698 <em>only</em> match in down-level clients. A CSS namespace aware
2699 client will match element type and attribute selectors based on
2700 the name's local part. Selectors declared with the fully
2701 qualified name will not match (unless there is no namespace prefix
2702 in the fully qualified name).</li>
2704 </ul>
2706 </li>
2708 </ol>
2710 <p>In other scenarios: when the namespace prefixes used in the XML are
2711 not known in advance by the style sheet author; or a combination of
2712 elements with no namespace are used in conjunction with elements using
2713 a default namespace; or the same namespace prefix is mapped to
2714 <em>different</em> namespace URIs within the same document, or in
2715 different documents; it is impossible to construct a CSS style sheet
2716 that will function properly against all elements in those documents,
2717 unless, the style sheet is written using a namespace URI syntax (as
2718 outlined in this document or similar) and the document is processed by
2719 a CSS and XML namespace aware client.</p>
2721 <h2><a name=profiling>12. Profiles</a></h2>
2723 <p>Each specification using Selectors must define the subset of W3C
2724 Selectors it allows and excludes, and describe the local meaning of
2725 all the components of that subset.</p>
2727 <p>Non normative examples:
2731 <tbody>
2732 <tr>
2734 <tr>
2735 <th>Specification</th>
2736 <td>CSS level 1</td></tr>
2737 <tr>
2738 <th>Accepts</th>
2739 <td>type selectors<br>class selectors<br>ID selectors<br>:link,
2740 :visited and :active pseudo-classes<br>descendant combinator
2741 <br>::first-line and ::first-letter pseudo-elements</td></tr>
2742 <tr>
2743 <th>Excludes</th>
2744 <td>
2746 <p>universal selector<br>attribute selectors<br>:hover and :focus
2747 pseudo-classes<br>:target pseudo-class<br>:lang() pseudo-class<br>all UI
2748 element states pseudo-classes<br>all structural
2749 pseudo-classes<br>negation pseudo-class<br>all
2750 UI element fragments pseudo-elements<br>::before and ::after
2751 pseudo-elements<br>child combinators<br>sibling combinators
2753 <p>namespaces</td></tr>
2754 <tr>
2755 <th>Extra constraints</th>
2756 <td>only one class selector allowed per sequence of simple
2757 selectors</td></tr></tbody></table><br><br>
2759 <tbody>
2760 <tr>
2762 <tr>
2763 <th>Specification</th>
2764 <td>CSS level 2</td></tr>
2765 <tr>
2766 <th>Accepts</th>
2767 <td>type selectors<br>universal selector<br>attribute presence and
2768 values selectors<br>class selectors<br>ID selectors<br>:link, :visited,
2769 :active, :hover, :focus, :lang() and :first-child pseudo-classes
2770 <br>descendant combinator<br>child combinator<br>adjacent sibling
2771 combinator<br>::first-line and ::first-letter pseudo-elements<br>::before
2772 and ::after pseudo-elements</td></tr>
2773 <tr>
2774 <th>Excludes</th>
2775 <td>
2777 <p>content selectors<br>substring matching attribute
2778 selectors<br>:target pseudo-classes<br>all UI element
2779 states pseudo-classes<br>all structural pseudo-classes other
2780 than :first-child<br>negation pseudo-class<br>all UI element
2781 fragments pseudo-elements<br>general sibling combinators
2783 <p>namespaces</td></tr>
2784 <tr>
2785 <th>Extra constraints</th>
2786 <td>more than one class selector per sequence of simple selectors (CSS1
2787 constraint) allowed</td></tr></tbody></table>
2789 <p>In CSS, selectors express pattern matching rules that determine which style
2790 rules apply to elements in the document tree.
2792 <p>The following selector (CSS level 2) will <b>match</b> all anchors <code>a</code>
2793 with attribute <code>name</code> set inside a section 1 header <code>h1</code>:
2794 <pre>h1 a[name]</pre>
2796 <p>All CSS declarations attached to such a selector are applied to elements
2797 matching it. </div>
2801 <tbody>
2802 <tr>
2804 <tr>
2805 <th>Specification</th>
2806 <td>STTS 3</td>
2807 </tr>
2808 <tr>
2809 <th>Accepts</th>
2810 <td>
2812 <p>type selectors<br>universal selectors<br>attribute selectors<br>class
2813 selectors<br>ID selectors<br>all structural pseudo-classes<br>
2814 all combinators
2816 <p>namespaces</td></tr>
2817 <tr>
2818 <th>Excludes</th>
2819 <td>non-accepted pseudo-classes<br>pseudo-elements<br></td></tr>
2820 <tr>
2821 <th>Extra constraints</th>
2822 <td>some selectors and combinators are not allowed in fragment
2823 descriptions on the right side of STTS declarations.</td></tr></tbody></table>
2824 <form>
2850 </form>
2852 <p>Selectors can be used in STTS 3 in two different
2853 manners:
2854 <ol>
2855 <li>a selection mechanism equivalent to CSS selection mechanism: declarations
2856 attached to a given selector are applied to elements matching that selector,
2857 <li>fragment descriptions that appear on the right side of declarations.
2858 </li></ol></div>
2860 <h2><a name=Conformance></a>13. Conformance and requirements</h2>
2862 <p>This section defines conformance with the present specification only.
2864 <p>The inability of a user agent to implement part of this specification due to
2865 the limitations of a particular device (e.g., non interactive user agents will
2866 probably not implement dynamic pseudo-classes because they make no sense without
2867 interactivity) does not imply non-conformance.
2869 <p>All specifications reusing Selectors must contain a <a
2871 subset of Selectors it accepts or excludes, and describing the constraints
2872 it adds to the current specification.
2874 <p>Invalidity is caused by a parsing error, e.g. an unrecognized token or a token
2875 which is not allowed at the current parsing point.
2877 <p>User agents must observe the rules for handling parsing errors:
2878 <ul>
2879 <li>a simple selector containing an undeclared namespace prefix is invalid</li>
2880 <li>a selector containing an invalid simple selector, an invalid combinator
2881 or an invalid token is invalid. </li>
2882 <li>a group of selectors containing an invalid selector is invalid.</li>
2883 </ul>
2886 errors. (In the case of CSS, the entire rule in which the selector is
2887 used is dropped.)</p>
2889 <!-- Apparently all these references are out of date:
2890 <p>Implementations of this specification must behave as
2892 when parsing selectors and attempting matches. (In particular,
2893 implementations must assume the data is normalized and must not
2894 normalize it.) Normative rules for matching strings are defined in
2897 specification.</p>-->
2899 <h2><a name=Tests></a>14. Tests</h2>
2901 <p>This specification has <a
2903 suite</a> allowing user agents to verify their basic conformance to
2904 the specification. This test suite does not pretend to be exhaustive
2905 and does not cover all possible combined cases of Selectors.</p>
2907 <h2><a name=ACKS></a>15. Acknowledgements</h2>
2909 <p>The CSS working group would like to thank everyone who has sent
2910 comments on this specification over the years.</p>
2912 <p>The working group would like to extend special thanks to Donna
2913 McManus, Justin Baker, Joel Sklar, and Molly Ives Brower who perfermed
2914 the final editorial review.</p>
2916 <h2><a name=references>16. References</a></h2>
2920 <dt>[CSS1]
2921 <dd><a name=refsCSS1></a> Bert Bos, Håkon Wium Lie; "<cite>Cascading Style Sheets, level 1</cite>", W3C Recommendation, 17 Dec 1996, revised 11 Jan 1999
2924 <dt>[CSS21]
2925 <dd><a name=refsCSS21></a> Bert Bos, Tantek Çelik, Ian Hickson, Håkon Wium Lie, editors; "<cite>Cascading Style Sheets, level 2 revision 1</cite>", W3C Working Draft, 13 June 2005
2928 <dt>[CWWW]
2929 <dd><a name=refsCWWW></a> Martin J. Dürst, François Yergeau, Misha Wolf, Asmus Freytag, Tex Texin, editors; "<cite>Character Model for the World Wide Web</cite>", W3C Recommendation, 15 February 2005
2932 <dt>[FLEX]
2933 <dd><a name="refsFLEX"></a> "<cite>Flex: The Lexical Scanner Generator</cite>", Version 2.3.7, ISBN 1882114213
2935 <dt>[HTML4]
2936 <dd><a name="refsHTML4"></a> Dave Ragget, Arnaud Le Hors, Ian Jacobs, editors; "<cite>HTML 4.01 Specification</cite>", W3C Recommendation, 24 December 1999
2939 <dt>[MATH]
2940 <dd><a name="refsMATH"></a> Patrick Ion, Robert Miner, editors; "<cite>Mathematical Markup Language (MathML) 1.01</cite>", W3C Recommendation, revision of 7 July 1999
2941 <dd>(<code><a href="http://www.w3.org/TR/REC-MathML/">http://www.w3.org/TR/REC-MathML/</a></code>)
2943 <dt>[RFC3066]
2944 <dd><a name="refsRFC3066"></a> H. Alvestrand; "<cite>Tags for the Identification of Languages</cite>", Request for Comments 3066, January 2001
2945 <dd>(<a href="http://www.ietf.org/rfc/rfc3066.txt"><code>http://www.ietf.org/rfc/rfc3066.txt</code></a>)
2947 <dt>[STTS]
2948 <dd><a name=refsSTTS></a> Daniel Glazman; "<cite>Simple Tree Transformation Sheets 3</cite>", Electricité de France, submission to the W3C, 11 November 1998
2949 <dd>(<code><a href="http://www.w3.org/TR/NOTE-STTS3">http://www.w3.org/TR/NOTE-STTS3</a></code>)
2951 <dt>[SVG]
2952 <dd><a name="refsSVG"></a> Jon Ferraiolo, 藤沢 淳, Dean Jackson, editors; "<cite>Scalable Vector Graphics (SVG) 1.1 Specification</cite>", W3C Recommendation, 14 January 2003
2955 <dt>[UNICODE]</dt>
2957 href="http://www.unicode.org/versions/Unicode4.1.0/">The Unicode Standard, Version 4.1</a></cite>, The Unicode Consortium. Boston, MA, Addison-Wesley, March 2005. ISBN 0-321-18578-1, as amended by <a href="http://www.unicode.org/versions/Unicode4.0.1/">Unicode 4.0.1</a> and <a href="http://www.unicode.org/versions/Unicode4.1.0/">Unicode 4.1.0</a>.
2958 <dd>(<code><a href="http://www.unicode.org/versions/">http://www.unicode.org/versions/</a></code>)</dd>
2960 <dt>[XML10]
2961 <dd><a name="refsXML10"></a> Tim Bray, Jean Paoli, C. M. Sperberg-McQueen, Eve Maler, François Yergeau, editors; "<cite>Extensible Markup Language (XML) 1.0 (Third Edition)</cite>", W3C Recommendation, 4 February 2004
2964 <dt>[XMLNAMES]
2965 <dd><a name="refsXMLNAMES"></a> Tim Bray, Dave Hollander, Andrew Layman, editors; "<cite>Namespaces in XML</cite>", W3C Recommendation, 14 January 1999
2966 <dd>(<a href="http://www.w3.org/TR/REC-xml-names/"><code>http://www.w3.org/TR/REC-xml-names/</code></a>)
2968 <dt>[YACC]
2969 <dd><a name="refsYACC"></a> S. C. Johnson; "<cite>YACC — Yet another compiler compiler</cite>", Technical Report, Murray Hill, 1975
2971 </dl>
2972 </body>
2973 </html>