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171 <body>
173 <p><a href="http://www.w3.org/"><img height=48 alt=W3C src="http://www.w3.org/Icons/w3c_home" width=72></a>
179 <dl>
181 <dt>This version:
186 <dt>Latest version:
189 http://www.w3.org/TR/css3-selectors</a>
191 <dt>Previous version:
200 <dd class="vcard"><a lang="tr" class="url fn" href="http://www.tantek.com/">Tantek Çelik</a> (Invited Expert)
208 <dd class="vcard"><span class="fn">John Williams</span> (former editor, <span class="company"><a
211 </dl>
222 <a
224 <a
226 <a
228 use</a> rules apply.
232 </div>
237 tree. Selectors have been optimized for use with HTML and XML, and
238 are designed to be usable in performance-critical code.</p>
241 Style Sheets) is a language for describing the rendering of <acronym
244 screen, on paper, in speech, etc. CSS uses Selectors for binding
245 style properties to elements in the document. This document
246 describes extensions to the selectors defined in CSS level 2. These
247 extended selectors will be used by CSS level 3.
253 <p>That is, given an element and a selector, this specification
254 defines whether that element matches the selector.</p>
256 <p>These expressions can also be used, for instance, to select a set
257 of elements, or a single element from a set of elements, by
258 evaluating the expression across all the elements in a
265 <p><em>This section describes the status of this document at the
266 time of its publication. Other documents may supersede this
267 document. A list of current W3C publications and the latest revision
268 of this technical report can be found in the <a
270 http://www.w3.org/TR/.</a></em></p>
278 <p>The CSS Working Group doesn't expect that all implementations of
279 CSS3 will have to implement all selectors. Instead, there will
280 probably be a small number of variants of CSS3, called profiles. For
281 example, it may be that only a profile for interactive user agents
282 will include all of the selectors.</p>
287 document is a revision of the <a
290 implementation feedback received in the past few years. It is
291 expected that this last call will proceed straight to Proposed
292 Recommendation stage since it is believed that interoperability will
293 be demonstrable.</p>
295 <p>All persons are encouraged to review and implement this
296 specification and return comments to the (<a
298 public mailing list <a
301 Members can also send comments directly to the CSS Working
302 Group.
305 <p>This is still a draft document and may be updated, replaced, or
306 obsoleted by other documents at any time. It is inappropriate to
311 The English version of this specification is the only normative
312 version.
320 <ul>
324 </ul>
334 </ul>
336 <ul>
338 </ul>
341 <li class="tocline4"><a href="#attribute-representation">6.3.1. Representation of attributes and attributes values</a>
345 </ul>
355 <ul>
368 </ul>
370 </ul>
371 </li>
372 </ul>
374 <ul>
379 </ul>
386 <li class="tocline4"><a href="#adjacent-sibling-combinators">8.3.1. Adjacent sibling combinator</a>
387 <li class="tocline4"><a href="#general-sibling-combinators">8.3.2. General sibling combinator</a></li>
388 </ul>
389 </li>
390 </ul>
396 </ul>
403 </ul>
405 </div>
411 <p>Some features of this specification are specific to CSS, or have
412 particular limitations or rules specific to CSS. In this
413 specification, these have been described in terms of CSS2.1. <a
418 <p>All of the text of this specification is normative except
419 examples, notes, and sections explicitly marked as
420 non-normative.</p>
426 <p>The main differences between the selectors in CSS2 and those in
427 Selectors are:
429 <ul>
431 <li>the list of basic definitions (selector, group of selectors,
432 simple selector, etc.) has been changed; in particular, what was
433 referred to in CSS2 as a simple selector is now called a sequence
434 of simple selectors, and the term "simple selector" is now used for
435 the components of this sequence</li>
437 <li>an optional namespace component is now allowed in type element
438 selectors, the universal selector and attribute selectors</li>
442 <li>new simple selectors including substring matching attribute
443 selectors, and new pseudo-classes</li>
446 for pseudo-elements</li>
450 <li>profiles to be added to specifications integrating Selectors
451 and defining the set of selectors which is actually supported by
452 each specification</li>
454 <li>Selectors are now a CSS3 Module and an independent
455 specification; other specifications can now refer to this document
456 independently of CSS</li>
460 </ul>
464 <p><em>This section is non-normative, as it merely summarizes the
465 following sections.</em></p>
467 <p>A Selector represents a structure. This structure can be used as a
468 condition (e.g. in a CSS rule) that determines which elements a
469 selector matches in the document tree, or as a flat description of the
470 HTML or XML fragment corresponding to that structure.</p>
472 <p>Selectors may range from simple element names to rich contextual
473 representations.</p>
478 <thead>
479 <tr>
484 <tbody>
485 <tr>
490 selector</a></td>
492 <tr>
498 <tr>
503 selectors</a></td>
505 <tr>
511 selectors</a></td>
513 <tr>
519 selectors</a></td>
521 <tr>
527 selectors</a></td>
529 <tr>
535 selectors</a></td>
537 <tr>
543 selectors</a></td>
545 <tr>
551 selectors</a></td>
553 <tr>
558 pseudo-classes</a></td>
560 <tr>
565 pseudo-classes</a></td>
567 <tr>
570 from the last one</td>
573 pseudo-classes</a></td>
575 <tr>
580 pseudo-classes</a></td>
582 <tr>
585 from the last one</td>
588 pseudo-classes</a></td>
590 <tr>
595 pseudo-classes</a></td>
597 <tr>
602 pseudo-classes</a></td>
604 <tr>
609 pseudo-classes</a></td>
611 <tr>
616 pseudo-classes</a></td>
618 <tr>
623 pseudo-classes</a></td>
625 <tr>
630 pseudo-classes</a></td>
632 <tr>
635 nodes)</td>
638 pseudo-classes</a></td>
640 <tr>
643 which the target is not yet visited (:link) or already visited
644 (:visited)</td>
647 pseudo-classes</a></td>
649 <tr>
654 action pseudo-classes</a></td>
656 <tr>
661 pseudo-class</a></td>
663 <tr>
666 language specifies how language is determined)</td>
669 pseudo-class</a></td>
671 <tr>
674 disabled</td>
677 pseudo-classes</a></td>
679 <tr>
685 pseudo-classes</a></td>
687 <tr>
692 pseudo-element</a></td>
694 <tr>
699 pseudo-element</a></td>
701 <tr>
704 selected/highlighted by the user</td>
707 fragments pseudo-elements</a></td>
709 <tr>
714 pseudo-element</a></td>
716 <tr>
721 pseudo-element</a></td>
723 <tr>
729 selectors</a></td>
731 <tr>
736 selectors</a></td>
738 <tr>
743 pseudo-class</a></td>
745 <tr>
750 combinator</a></td>
752 <tr>
757 combinator</a></td>
759 <tr>
765 <tr>
772 <p>The meaning of each selector is derived from the table above by
774 column.</p>
778 <p>The case sensitivity of document language element names, attribute
779 names, and attribute values in selectors depends on the document
780 language. For example, in HTML, element names are case-insensitive,
781 but in XML, they are case-sensitive.</p>
794 selector or universal selector is allowed in the sequence.</p>
806 sequence of simple selectors.</p>
811 space may appear between a combinator and the simple selectors around
816 never part of white space.</p>
818 <p>The elements of a document tree that are represented by a selector
820 selector consisting of a single sequence of simple selectors
821 represents any element satisfying its requirements. Prepending another
822 sequence of simple selectors and a combinator to a sequence imposes
823 additional matching constraints, so the subjects of a selector are
824 always a subset of the elements represented by the last sequence of
825 simple selectors.</p>
827 <p>An empty selector, containing no sequence of simple selectors and
833 <p>When several selectors share the same declarations, they may be
838 <p>In this example, we condense three rules with identical
839 declarations into one. Thus,</p>
840 <pre>h1 { font-family: sans-serif }
841 h2 { font-family: sans-serif }
842 h3 { font-family: sans-serif }</pre>
845 </div>
848 because all the selectors are valid selectors. If just one of these
849 selectors were invalid, the entire group of selectors would be
850 invalid. This would invalidate the rule for all three heading
851 elements, whereas in the former case only one of the three individual
852 heading rules would be invalidated.</p>
860 element type. A type selector represents an instance of the element
861 type in the document tree.</p>
867 </div>
874 that has been previously declared may be prepended to the element name
878 <p>The namespace component may be left empty to indicate that the
879 selector is only to represent elements with no declared namespace.</p>
881 <p>An asterisk may be used for the namespace prefix, indicating that
882 the selector represents elements in any namespace (including elements
883 with no namespace).</p>
885 <p>Element type selectors that have no namespace component (no
886 namespace separator), represent elements without regard to the
887 element's namespace (equivalent to "<code>*|</code>") unless a default
888 namespace has been declared. If a default namespace has been declared,
889 the selector will represent only elements in the default
890 namespace.</p>
892 <p>A type selector containing a namespace prefix that has not been
894 The mechanism for declaring a namespace prefix is left up to the
895 language implementing Selectors. In CSS, such a mechanism is defined
896 in the General Syntax module.</p>
898 <p>In a namespace-aware client, element type selectors will only match
899 against the <a
901 of the element's <a
904 behaviors in down-level clients.</p>
908 <dl>
912 <dd>elements with name E in any namespace, including those without any
913 declared namespace</dd>
917 <dd>if no default namespace has been specified, this is equivalent to *|E.
918 Otherwise it is equivalent to ns|E where ns is the default namespace.</dd>
919 </dl>
924 <pre>@namespace foo url(http://www.example.com);
925 foo|h1 { color: blue }
926 foo|* { color: yellow }
927 |h1 { color: red }
928 *|h1 { color: green }
929 h1 { color: green }</pre>
934 <p>The second rule will match all elements in the
938 any declared namespace.</p>
941 namespace (including those without any declared namespace).</p>
943 <p>The last rule is equivalent to the fourth rule because no default
944 namespace has been defined.</p>
946 </div>
952 type. It represents any single element in the document tree in any
953 namespace (including those without any declared namespace) if no
954 default namespace has been specified. If a default namespace has been
958 <p>If the universal selector is not the only component of a sequence
963 <ul>
967 </ul>
968 </div>
972 omitted.</p>
976 <p>The universal selector allows an optional namespace component. It
977 is used as follows:</p>
979 <dl>
987 <dd>if no default namespace has been specified, this is equivalent to *|*.
988 Otherwise it is equivalent to ns|* where ns is the default namespace.</dd>
989 </dl>
991 <p>A universal selector containing a namespace prefix that has not
993 selector. The mechanism for declaring a namespace prefix is left up
994 to the language implementing Selectors. In CSS, such a mechanism is
995 defined in the General Syntax module.</p>
1000 <p>Selectors allow the representation of an element's attributes. When
1001 a selector is used as an expression to match against an element,
1002 attribute selectors must be considered to match an element if that
1003 element has an attribute that matches the attribute represented by the
1004 attribute selector.</p>
1007 selectors</a></h4>
1011 <dl>
1014 the attribute.</dd>
1023 spaces).</dd>
1033 </dl>
1035 <p>Attribute values must be identifiers or strings. The
1036 case-sensitivity of attribute names and values in selectors depends on
1037 the document language.</p>
1045 value:</p>
1049 <p>In the following example, the selector represents a
1055 <p>Multiple attribute selectors can be used to represent several
1056 attributes of an element, or several conditions on the same
1065 and "~=". The first selector will represent, for example, the value
1085 <p>Similarly, the following selectors represents a
1089 <pre>DIALOGUE[character=romeo]
1090 DIALOGUE[character=juliet]</pre>
1092 </div>
1095 selectors</h4>
1097 <p>Three additional attribute selectors are provided for matching
1098 substrings in the value of an attribute:</p>
1100 <dl>
1110 </dl>
1112 <p>Attribute values must be identifiers or strings. The
1113 case-sensitivity of attribute names in selectors depends on the
1114 document language.</p>
1119 image:</p>
1127 </div>
1131 <p>Attribute selectors allow an optional namespace component to the
1132 attribute name. A namespace prefix that has been previously declared
1133 may be prepended to the attribute name separated by the namespace
1135 the Namespaces in the XML recommendation, default namespaces do not
1136 apply to attributes, therefore attribute selectors without a namespace
1137 component apply only to attributes that have no declared namespace
1138 (equivalent to "<code>|attr</code>"). An asterisk may be used for the
1139 namespace prefix indicating that the selector is to match all
1140 attribute names without regard to the attribute's namespace.
1142 <p>An attribute selector with an attribute name containing a namespace
1143 prefix that has not been previously declared is an <a
1145 a namespace prefix is left up to the language implementing Selectors.
1146 In CSS, such a mechanism is defined in the General Syntax module.
1151 [foo|att=val] { color: blue }
1152 [*|att] { color: yellow }
1153 [|att] { color: green }
1154 [att] { color: green }</pre>
1156 <p>The first rule will match only elements with the attribute
1160 <p>The second rule will match only elements with the attribute
1162 (including no declared namespace).</p>
1164 <p>The last two rules are equivalent and will match only elements
1166 declared to be in a namespace.</p>
1168 </div>
1172 <p>Attribute selectors represent explicitly set attribute values in
1173 the document tree. Default attribute values may be defined in a DTD or
1174 elsewhere, but cannot always be selected by attribute
1175 selectors. Selectors should be designed so that they work even if the
1176 default values are not included in the document tree.</p>
1185 knowledge of that namespace to treat default attribute values as if
1186 they were present in the document. (For example, an XHTML UA is not
1187 required to use its built-in knowledge of the XHTML DTD.)</p>
1190 choose to ignore external subsets.</p>
1202 <pre>EXAMPLE[notation=decimal] { /*... default property settings ...*/ }
1203 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1206 is set by default, i.e. not set explicitly. To catch all cases, the
1207 attribute selector for the default value must be dropped:</p>
1209 <pre>EXAMPLE { /*... default property settings ...*/ }
1210 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1213 more specific than the tag
1214 selector alone, the style declarations in the second rule will override
1215 those in the first for elements that have a "notation" attribute value
1216 of "octal". Care has to be taken that all property declarations that
1217 are to apply only to the default case are overridden in the non-default
1218 cases' style rules.</p>
1220 </div>
1228 the same meaning. The attribute value must immediately follow the
1231 <p>UAs may apply selectors using the period (.) notation in XML
1232 documents if the UA has namespace-specific knowledge that allows it to
1234 respective namespace. One such example of namespace-specific knowledge
1235 is the prose in the specification for a particular namespace (e.g. SVG
1246 <p>We can assign style information to all elements with
1255 <p>The following assigns style only to H1 elements with
1260 <p>Given these rules, the first H1 instance below would not have
1261 green text, while the second would:</p>
1266 </div>
1276 has been assigned a list of <a
1286 </div>
1289 power to the "class" attribute, authors could conceivably design their
1290 own "document language" based on elements with almost no associated
1291 presentation (such as DIV and SPAN in HTML) and assigning style
1292 information through the "class" attribute. Authors should avoid this
1293 practice since the structural elements of a document language often
1294 have recognized and accepted meanings and author-defined classes may
1295 not.</p>
1298 class attributes, their values must be concatenated with spaces
1299 between the values before searching for the class. As of this time the
1300 working group is not aware of any manner in which this situation can
1301 be reached, however, so this behavior is explicitly non-normative in
1302 this specification.</p>
1306 <p>Document languages may contain attributes that are declared to be
1307 of type ID. What makes attributes of type ID special is that no two
1308 such attributes can have the same value in a document, regardless of
1309 the type of the elements that carry them; whatever the document
1310 language, an ID typed attribute can be used to uniquely identify its
1311 element. In HTML all ID attributes are named "id"; XML applications
1312 may name ID attributes differently, but the same restriction
1313 applies.</p>
1315 <p>An ID-typed attribute of a document language allows authors to
1316 assign an identifier to one element instance in the document tree. W3C
1317 ID selectors represent an element instance based on its identifier. An
1320 identifier.</p>
1322 <p>Selectors does not specify how a UA knows the ID-typed attribute of
1323 an element. The UA may, e.g., read a document's DTD, have the
1324 information hard-coded or ask the user.
1331 <p>The following ID selector represents any element whose ID-typed
1334 <p>The following selector represents any element whose ID-typed
1337 </div>
1341 contains an element's IDs is contained in a DTD or a schema. When
1342 parsing XML, UAs do not always read the DTD, and thus may not know
1343 what the ID of an element is (though a UA may have namespace-specific
1344 knowledge that allows it to determine which attribute is the ID
1345 attribute for that namespace). If a style sheet designer knows or
1346 suspects that a UA may not know what the ID of an element is, he
1347 should use normal attribute selectors instead:
1351 <p>If an element has multiple ID attributes, all of them must be
1352 treated as IDs for that element for the purposes of the ID
1353 selector. Such a situation could be reached using mixtures of xml:id,
1354 DOM3 Core, XML DTDs, and namespace-specific knowledge.</p>
1358 <p>The pseudo-class concept is introduced to permit selection based on
1359 information that lies outside of the document tree or that cannot be
1360 expressed using the other simple selectors.</p>
1364 optionally by a value between parentheses.</p>
1366 <p>Pseudo-classes are allowed in all sequences of simple selectors
1367 contained in a selector. Pseudo-classes are allowed anywhere in
1368 sequences of simple selectors, after the leading type selector or
1369 universal selector (possibly omitted). Pseudo-class names are
1370 case-insensitive. Some pseudo-classes are mutually exclusive, while
1371 others can be applied simultaneously to the same
1372 element. Pseudo-classes may be dynamic, in the sense that an element
1373 may acquire or lose a pseudo-class while a user interacts with the
1374 document.</p>
1379 <p>Dynamic pseudo-classes classify elements on characteristics other
1380 than their name, attributes, or content, in principle characteristics
1381 that cannot be deduced from the document tree.</p>
1383 <p>Dynamic pseudo-classes do not appear in the document source or
1384 document tree.</p>
1389 <p>User agents commonly display unvisited links differently from
1390 previously visited ones. Selectors
1394 <ul>
1396 not yet been visited.</li>
1398 been visited by the user. </li>
1399 </ul>
1401 <p>After some amount of time, user agents may choose to return a
1402 visited link to the (unvisited) ':link' state.</p>
1410 <p>The following selector represents links carrying class
1415 </div>
1418 authors to abuse the :link and :visited pseudo-classes to determine
1419 which sites a user has visited without the user's consent.
1421 <p>UAs may therefore treat all links as unvisited links, or implement
1422 other measures to preserve the user's privacy while rendering visited
1423 and unvisited links differently.</p>
1426 :hover, :active, and :focus</a></h5>
1428 <p>Interactive user agents sometimes change the rendering in response
1429 to user actions. Selectors provides
1430 three pseudo-classes for the selection of an element the user is
1431 acting on.</p>
1433 <ul>
1436 designates an element with a pointing device, but does not activate
1437 it. For example, a visual user agent could apply this pseudo-class
1438 when the cursor (mouse pointer) hovers over a box generated by the
1439 element. User agents not that do not support <a
1441 media</a> do not have to support this pseudo-class. Some conforming
1442 user agents that support <a
1444 media</a> may not be able to support this pseudo-class (e.g., a pen
1445 device that does not detect hovering).</li>
1448 is being activated by the user. For example, between the times the
1449 user presses the mouse button and releases it.</li>
1452 has the focus (accepts keyboard or mouse events, or other forms of
1453 input). </li>
1455 </ul>
1457 <p>There may be document language or implementation specific limits on
1461 <p>These pseudo-classes are not mutually exclusive. An element may
1462 match several pseudo-classes at the same time.</p>
1464 <p>Selectors doesn't define if the parent of an element that is
1465 ':active' or ':hover' is also in that state.</p>
1469 <pre>a:link /* unvisited links */
1470 a:visited /* visited links */
1471 a:hover /* user hovers */
1472 a:active /* active links */</pre>
1474 <pre>a:focus
1475 a:focus:hover</pre>
1477 the pseudo-class :focus and in the pseudo-class :hover.</p>
1478 </div>
1481 and ':active' (or ':link' and ':active').</p>
1485 <p>Some URIs refer to a location within a resource. This kind of URI
1487 identifier (called the fragment identifier).</p>
1489 <p>URIs with fragment identifiers link to a certain element within the
1490 document, known as the target element. For instance, here is a URI
1492 document:</p>
1497 pseudo-class. If the document's URI has no fragment identifier, then
1498 the document has no target element.</p>
1505 URI.</p>
1506 </div>
1511 target element red and place an image before it, if there is one:</p>
1512 <pre>*:target { color : red }
1513 *:target::before { content : url(target.png) }</pre>
1514 </div>
1518 <p>If the document language specifies how the human language of an
1519 element is determined, it is possible to write selectors that
1520 represent an element based on its language. For example, in HTML <a
1523 element, and possibly by information from the protocol (such as HTTP
1525 there may be other document language-specific methods for determining
1526 the language.</p>
1529 is in language C. Whether an element is represented by a
1531 being either equal to, or a hyphen-separated substring of, the
1532 element's language value, in the same way as if performed by the <a
1534 selectors. The identifier C does not have to be a valid language
1535 name.</p>
1549 <p>The two following selectors represent an HTML document that is in
1550 Belgian, French, or German. The two next selectors represent
1552 or German.</p>
1553 <pre>html:lang(fr-be)
1554 html:lang(de)
1555 :lang(fr-be) > q
1557 </div>
1564 the look of user interface elements that are enabled — which the
1565 user can select or activate in some fashion (e.g. clicking on a button
1566 with a mouse). There is a need for such a pseudo-class because there
1567 is no way to programmatically specify the default appearance of say,
1569 would look like when it was disabled.</p>
1572 author to specify precisely how a disabled or inactive user interface
1573 element should look.</p>
1575 <p>Most elements will be neither enabled nor disabled. An element is
1576 enabled if the user can either activate it or transfer the focus to
1577 it. An element is disabled if it could be enabled, but the user cannot
1578 presently activate it or transfer focus to it.</p>
1583 <p>Radio and checkbox elements can be toggled by the user. Some menu
1584 items are "checked" when the user selects them. When such elements are
1588 attributes as described in <a
1593 in nature, and is altered by user action, since it can also be based
1602 <p>Radio and checkbox elements can be toggled by the user, but are
1603 sometimes in an indeterminate state, neither checked nor unchecked.
1604 This can be due to an element attribute, or DOM manipulation.</p>
1606 <p>A future version of this specification may introduce an
1608 <!--While the <code>:indeterminate</code> pseudo-class is dynamic in
1609 nature, and is altered by user action, since it can also be based on
1610 the presence of an element attribute, it applies to all media.</p>
1612 <p>Components of a radio-group initialized with no pre-selected choice
1615 </div>
1621 pseudo-classes</dfn> to permit selection based on extra information that lies in
1622 the document tree but cannot be represented by other simple selectors or
1623 combinators.
1625 <p>Note that standalone pieces of PCDATA (text nodes in the DOM) are
1626 not counted when calculating the position of an element in the list of
1627 children of its parent. When calculating the position of an element in
1628 the list of children of its parent, the index numbering starts at 1.
1634 the root of the document. In HTML 4, this is always the
1640 <p>The
1642 pseudo-class notation represents an element that has
1648 each. For example, this allows the selectors to address every other
1649 row in a table, and could be used to alternate the color
1652 integers. The index of the first child of an element is 1.
1663 tr:nth-child(odd) /* same */
1664 tr:nth-child(2n) /* represents every even row of an HTML table */
1665 tr:nth-child(even) /* same */
1667 /* Alternate paragraph colours in CSS */
1672 </div>
1677 included, so the syntax simplifies to
1685 </div>
1693 bar:nth-child(n+0) /* same */
1694 bar:nth-child(n) /* same */
1696 </div>
1705 </div>
1708 pseudo-class represents no element in the document tree.</p>
1713 tree.</p>
1718 </div>
1721 expression must be removed (it is effectively replaced by the "-"
1729 </div>
1735 pseudo-class notation represents an element that has
1741 as arguments.
1748 foo:nth-last-child(odd) /* represents all odd foo elements in their parent element,
1749 counting from the last one */</pre>
1750 </div>
1756 pseudo-class notation represents an element that has
1761 of that type after all the children of that type have been split into
1763 for the syntax of its argument. It also accepts the
1772 </div>
1778 pseudo-class notation represents an element that has
1790 following selector:</p>
1793 selector ends up being just as long:</p>
1795 </div>
1801 represents an element that is the first child of some other element.
1815 fragment:
1823 a:first-child /* Same (assuming a is not the root element) */</pre>
1824 </div>
1829 represents an element that is the last child of some other element.
1836 </div>
1841 represents an element that is the first sibling of its type in the list of
1842 children of its parent element.
1846 <p>The following selector represents a definition title
1849 its parent element.</p>
1852 elements in the following example but not for the third one:</p>
1864 </div>
1870 the last sibling of its type in the list of children of its parent
1871 element.</p>
1875 <p>The following selector represents the last data cell
1878 </div>
1882 <p>Represents an element that has a parent element and whose parent
1883 element has no other element children. Same as
1886 specificity.</p>
1890 <p>Represents an element that has a parent element and whose parent
1891 element has no other element children with the same element name. Same
1894 specificity.</p>
1900 no children at all. In terms of the DOM, only element nodes and text
1901 nodes (including CDATA nodes and entity references) whose data has a
1902 non-zero length must be considered as affecting emptiness; comments,
1903 PIs, and other nodes must not affect whether an element is considered
1904 empty or not.</p>
1911 following fragments:</p>
1915 </div>
1917 <h4><a name=content-selectors>6.6.6. Blank</a></h4> <!-- It's the Return of Appendix H!!! Run away! -->
1920 <!-- (used to be :contains()) -->
1926 selector</a> (excluding the negation pseudo-class itself and
1927 pseudo-elements) as an argument. It represents an element that is not
1928 represented by the argument.
1930 <!-- pseudo-elements are not simple selectors, so the above paragraph
1931 may be a bit confusing -->
1936 elements in an HTML document that are not disabled.</p>
1939 elements.</p>
1941 <p>The following group of selectors represents all HTML elements
1942 except links.</p>
1944 </div>
1946 <p>Default namespace declarations do not affect the argument of the
1947 negation pseudo-class unless the argument is a universal selector or a
1948 type selector.</p>
1952 <p>Assuming that the default namespace is bound to
1953 "http://example.com/", the following selector represents all
1954 elements that are not in that namespace:</p>
1956 <p>The following CSS selector matches any element being hovered,
1957 regardless of its namespace. In particular, it is not limited to
1958 only matching elements in the default namespace that are not being
1959 hovered, and elements not in the default namespace don't match the
1962 </div>
1968 specificity.</p>
1972 <p>Pseudo-elements create abstractions about the document tree beyond
1973 those specified by the document language. For instance, document
1974 languages do not offer mechanisms to access the first letter or first
1975 line of an element's content. Pseudo-elements allow designers to refer
1976 to this otherwise inaccessible information. Pseudo-elements may also
1977 provide designers a way to refer to content that does not exist in the
1980 content).</p>
1983 by the name of the pseudo-element.</p>
1986 in order to establish a discrimination between pseudo-classes and
1987 pseudo-elements. For compatibility with existing style sheets, user
1988 agents must also accept the previous one-colon notation for
1994 <p>Only one pseudo-element may appear per selector, and if present it
1995 must appear after the sequence of simple selectors that represents the
1997 future version of this specification may allow multiple
1998 pesudo-elements per selector.</span></p>
2003 of the first formatted line of an element.
2010 </div>
2013 HTML element. It does match a pseudo-element that conforming user
2014 agents will insert at the beginning of every paragraph.</p>
2016 <p>Note that the length of the first line depends on a number of
2017 factors, including the width of the page, the font size, etc. Thus,
2018 an ordinary HTML paragraph such as:</p>
2020 <pre>
2022 paragraph that will be broken into several
2023 lines. The first line will be identified
2024 by a fictional tag sequence. The other lines
2025 will be treated as ordinary lines in the
2027 </pre>
2029 <p>the lines of which happen to be broken as follows:
2031 <pre>
2032 THIS IS A SOMEWHAT LONG HTML PARAGRAPH THAT
2033 will be broken into several lines. The first
2034 line will be identified by a fictional tag
2035 sequence. The other lines will be treated as
2036 ordinary lines in the paragraph.
2037 </pre>
2041 fictional tag sequence helps to show how properties are inherited.</p>
2043 <pre>
2046 lines. The first line will be identified
2047 by a fictional tag sequence. The other lines
2048 will be treated as ordinary lines in the
2050 </pre>
2052 <p>If a pseudo-element breaks up a real element, the desired effect
2053 can often be described by a fictional tag sequence that closes and
2054 then re-opens the element. Thus, if we mark up the previous paragraph
2057 <pre>
2059 paragraph that will be broken into several
2061 by a fictional tag sequence. The other lines
2062 will be treated as ordinary lines in the
2064 </pre>
2066 <p>the user agent could simulate start and end tags for
2070 <pre>
2072 somewhat long HTML
2073 paragraph that will <b></SPAN></b></P::first-line><b><SPAN class="test"></b> be
2074 broken into several
2076 by a fictional tag sequence. The other lines
2077 will be treated as ordinary lines in the
2079 </pre>
2082 attached to a block-level element, an inline-block, a table-caption,
2083 or a table-cell.</p>
2086 element may occur inside a
2087 block-level descendant in the same flow (i.e., a block-level
2088 descendant that is not positioned and not a float). E.g., the first
2093 <p>The first line of a table-cell or inline-block cannot be the first
2104 <p>A UA should act as if the fictional start tags of the
2106 innermost enclosing block-level element. (Since CSS1 and CSS2 were
2107 silent on this case, authors should not rely on this behavior.) Here
2108 is an example. The fictional tag sequence for</p>
2110 <pre>
2115 </pre>
2119 <pre>
2121 <P><DIV::first-line><P::first-line>First paragraph</P::first-line></DIV::first-line></P>
2124 </pre>
2127 inline-level element, but with certain restrictions. In CSS, the
2129 pseudo-element: font properties, color property, background
2130 properties, 'word-spacing', 'letter-spacing', 'text-decoration',
2131 'vertical-align', 'text-transform', 'line-height'. UAs may apply other
2132 properties as well.</p>
2138 letter of the first line of a block, if it is not preceded by any
2139 other content (such as images or inline tables) on its line. The
2141 caps", which are common typographical effects. This type of initial
2142 letter is similar to an inline-level element if its 'float' property
2143 is 'none'; otherwise, it is similar to a floated element.</p>
2146 pseudo-elements: font properties, 'text-decoration', 'text-transform',
2147 'letter-spacing', 'word-spacing' (when appropriate), 'line-height',
2148 'float', 'vertical-align' (only if 'float' is 'none'), margin
2149 properties, padding properties, border properties, color property,
2150 background properties. UAs may apply other properties as well. To
2151 allow UAs to render a typographically correct drop cap or initial cap,
2152 the UA may choose a line-height, width and height based on the shape
2153 of the letter, unlike for normal elements.</p>
2157 <p>This example shows a possible rendering of an initial cap. Note
2159 pseudo-element is 1.1, but the UA in this example has computed the
2160 height of the first letter differently, so that it doesn't cause any
2161 unnecessary space between the first two lines. Also note that the
2164 <pre>
2165 p { line-height: 1.1 }
2166 p::first-letter { font-size: 3em; font-weight: normal }
2167 span { font-weight: bold }
2168 ...
2172 En dagelix geschrey de bange stad ontzet.
2173 </pre>
2176 </div>
2177 </div>
2182 <pre>
2189 P::first-letter { font-size: 200%; font-weight: bold; float: left }
2190 SPAN { text-transform: uppercase }
2198 </pre>
2203 <P><img src="first-letter.gif" alt="Image illustrating the combined effect of the ::first-letter and ::first-line pseudo-elements"></p>
2204 </div>
2209 <pre>
2213 T
2216 few words of an article in the Economist.
2218 </pre>
2221 the content (i.e., the initial character), while the ::first-line
2222 pseudo-element start tag is inserted right after the start tag of the
2223 block element.</p> </div>
2225 <p>In order to achieve traditional drop caps formatting, user agents
2226 may approximate font sizes, for example to align baselines. Also, the
2227 glyph outline may be taken into account when formatting.</p>
2231 punctuation classes), that precedes or follows the first letter should
2237 </div>
2244 block, list-item, table-cell, table-caption, and inline-block
2246 may allow this pesudo-element to apply to more element
2247 types.</span></p>
2250 such elements that contain text, or that have a descendant in the same
2251 flow that contains text. A UA should act as if the fictional start tag
2252 of the ::first-letter pseudo-element is just before the first text of
2253 the element, even if that first text is in a descendant.</p>
2257 <p>The fictional tag sequence for this HTMLfragment:
2260 <p>is:
2263 </div>
2265 <p>The first letter of a table-cell or inline-block cannot be the
2278 <p>In CSS, if an element is a list item ('display: list-item'), the
2280 principal box after the marker. UAs may ignore
2290 </div>
2292 <p>Some languages may have specific rules about how to treat certain
2293 letter combinations. In Dutch, for example, if the letter combination
2294 "ij" appears at the beginning of a word, both letters should be
2297 <p>If the letters that would form the ::first-letter are not in the
2299 may create a ::first-letter pseudo-element from one of the elements,
2300 both elements, or simply not create a pseudo-element.</p>
2302 <p>Similarly, if the first letter(s) of the block are not at the start
2303 of the line (for example due to bidirectional reordering), then the UA
2304 need not create the pseudo-element(s).
2309 how overlapping pseudo-elements may interact. The first letter of
2310 each P element will be green with a font size of '24pt'. The rest of
2311 the first formatted line will be 'blue' while the rest of the
2312 paragraph will be 'red'.</p>
2315 p::first-letter { color: green; font-size: 200% }
2316 p::first-line { color: blue }
2327 S
2330 ends up on two lines
2337 </div>
2343 of a document that has been highlighted by the user. This also
2344 applies, for example, to selected text within an editable text
2345 field. This pseudo-element should not be confused with the <code><a
2350 nature, and is altered by user action, it is reasonable to expect that
2351 when a UA re-renders to a static medium (such as a printed page, see
2353 dynamic medium (like screen), the UA may wish to transfer the current
2355 appropriate formatting and rendering take effect as well. This is not
2357 pseudo-element for static media.
2360 pseudo-elements: color, background, cursor (optional), outline
2361 (optional). The computed value of the 'background-image' property on
2368 can be used to describe generated content before or after an element's
2375 element including the inserted text.</p>
2381 <p>At times, authors may want selectors to describe an element that is
2382 the descendant of another element in the document tree (e.g., "an
2383 <code>EM</code> element that is contained within an <code>H1</code>
2384 element"). Descendant combinators express such a relationship. A
2386 separates two sequences of simple selectors. A selector of the form
2396 description of the following fragment:</p>
2403 either side of the "*" is not part of the universal selector; the
2404 whitespace is a combinator indicating that the DIV must be the
2405 ancestor of some element, and that that element must be an ancestor
2406 of the P.</p>
2407 <p>The following selector, which combines descendant combinators and
2412 </div>
2417 between two elements. A child combinator is made of the
2419 separates two sequences of simple selectors.
2427 <p>The following example combines descendant combinators and child
2428 combinators.</p>
2435 </div>
2437 <p>For information on selecting the first child of an element, please
2438 see the section on the <code><a
2440 above.</p>
2444 <p>There are two different sibling combinators: the adjacent sibling
2445 combinator and the general sibling combinator. In both cases,
2446 non-element nodes (e.g. text between elements) are ignored when
2447 considering adjacency of elements.</p>
2453 sequences of simple selectors. The elements represented by the two
2454 sequences share the same parent in the document tree and the element
2455 represented by the first sequence immediately precedes the element
2456 represented by the second one.</p>
2463 <p>The following selector is conceptually similar to the one in the
2464 previous example, except that it adds an attribute selector — it
2468 </div>
2475 simple selectors. The elements represented by the two sequences share
2476 the same parent in the document tree and the element represented by
2477 the first sequence precedes (not necessarily immediately) the element
2478 represented by the second one.</p>
2484 is a correct and valid, but partial, description of:</p>
2488 </div>
2494 <ul>
2496 <li>count the number of class selectors, attributes selectors, and pseudo-classes in the selector (= b)</li>
2499 </ul>
2502 are counted like any other, but the negation itself does not count as
2503 a pseudo-class.</p>
2505 <p>Concatenating the three numbers a-b-c (in a number system with a
2506 large base) gives the specificity.</p>
2519 </pre>
2520 </div>
2530 <p>The grammar below defines the syntax of Selectors. It is globally
2532 it directly, since it doesn't express the parsing conventions). The
2533 format of the productions is optimized for human consumption and some
2535 are used:</p>
2537 <ul>
2543 </ul>
2547 <pre>selectors_group
2548 : selector [ COMMA S* selector ]*
2549 ;
2551 selector
2552 : simple_selector_sequence [ combinator simple_selector_sequence ]*
2553 ;
2555 combinator
2556 /* combinators can be surrounded by white space */
2557 : PLUS S* | GREATER S* | TILDE S* | S+
2558 ;
2560 simple_selector_sequence
2561 : [ type_selector | universal ]
2562 [ HASH | class | attrib | pseudo | negation ]*
2563 | [ HASH | class | attrib | pseudo | negation ]+
2564 ;
2566 type_selector
2567 : [ namespace_prefix ]? element_name
2568 ;
2570 namespace_prefix
2571 : [ IDENT | '*' ]? '|'
2572 ;
2574 element_name
2575 : IDENT
2576 ;
2578 universal
2579 : [ namespace_prefix ]? '*'
2580 ;
2582 class
2583 : '.' IDENT
2584 ;
2586 attrib
2587 : '[' S* [ namespace_prefix ]? IDENT S*
2588 [ [ PREFIXMATCH |
2589 SUFFIXMATCH |
2590 SUBSTRINGMATCH |
2591 '=' |
2592 INCLUDES |
2593 DASHMATCH ] S* [ IDENT | STRING ] S*
2594 ]? ']'
2595 ;
2597 pseudo
2598 /* '::' starts a pseudo-element, ':' a pseudo-class */
2599 /* Exceptions: :first-line, :first-letter, :before and :after. */
2600 /* Note that pseudo-elements are restricted to one per selector and */
2601 /* occur only in the last simple_selector_sequence. */
2602 : ':' ':'? [ IDENT | functional_pseudo ]
2603 ;
2605 functional_pseudo
2606 : FUNCTION S* expression ')'
2607 ;
2609 expression
2610 /* In CSS3, the expressions are identifiers, strings, */
2611 /* or of the form "an+b" */
2612 : [ [ PLUS | '-' | DIMENSION | NUMBER | STRING | IDENT ] S* ]+
2613 ;
2615 negation
2616 : NOT S* negation_arg S* ')'
2617 ;
2619 negation_arg
2620 : type_selector | universal | HASH | class | attrib | pseudo
2621 ;</pre>
2628 case-insensitive.</p>
2631 number that current versions of Flex can deal with (decimal 255). They
2636 <pre>%option case-insensitive
2638 ident [-]?{nmstart}{nmchar}*
2639 name {nmchar}+
2640 nmstart [_a-z]|{nonascii}|{escape}
2643 escape {unicode}|\\[^\n\r\f0-9a-f]
2644 nmchar [_a-z0-9-]|{nonascii}|{escape}
2646 string {string1}|{string2}
2648 string2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*\'
2649 invalid {invalid1}|{invalid2}
2651 invalid2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*
2652 nl \n|\r\n|\r|\f
2653 w [ \t\r\n\f]*
2655 %%
2657 [ \t\r\n\f]+ return S;
2664 {ident} return IDENT;
2665 {string} return STRING;
2667 {num} return NUMBER;
2674 @{ident} return ATKEYWORD;
2675 {invalid} return INVALID;
2676 {num}% return PERCENTAGE;
2677 {num}{ident} return DIMENSION;
2683 U\+[0-9a-f?]{1,6}(-[0-9a-f]{1,6})? return UNICODE_RANGE;
2685 \/\*[^*]*\*+([^/*][^*]*\*+)*\/ /* ignore comments */
2687 . return *yytext;</pre>
2691 <h2><a name=downlevel>11. Namespaces and down-level clients</a></h2>
2693 <p>An important issue is the interaction of CSS selectors with XML
2694 documents in web clients that were produced prior to this
2695 document. Unfortunately, due to the fact that namespaces must be
2696 matched based on the URI which identifies the namespace, not the
2697 namespace prefix, some mechanism is required to identify namespaces in
2698 CSS by their URI as well. Without such a mechanism, it is impossible
2699 to construct a CSS style sheet which will properly match selectors in
2700 all cases against a random set of XML documents. However, given
2701 complete knowledge of the XML document to which a style sheet is to be
2702 applied, and a limited use of namespaces within the XML document, it
2703 is possible to construct a style sheet in which selectors would match
2704 elements and attributes correctly.</p>
2706 <p>It should be noted that a down-level CSS client will (if it
2707 properly conforms to CSS forward compatible parsing rules) ignore all
2708 <code>@namespace</code> at-rules, as well as all style rules that make
2709 use of namespace qualified element type or attribute selectors. The
2710 syntax of delimiting namespace prefixes in CSS was deliberately chosen
2711 so that down-level CSS clients would ignore the style rules rather
2712 than possibly match them incorrectly.</p>
2714 <p>The use of default namespaces in CSS makes it possible to write
2715 element type selectors that will function in both namespace aware CSS
2716 clients as well as down-level clients. It should be noted that
2717 down-level clients may incorrectly match selectors against XML
2718 elements in other namespaces.</p>
2720 <p>The following are scenarios and examples in which it is possible to
2721 construct style sheets which would function properly in web clients
2722 that do not implement this proposal.</p>
2724 <ol>
2725 <li>
2727 <p>The XML document does not use namespaces.</p>
2729 <ul>
2731 <li>In this case, it is obviously not necessary to declare or use
2732 namespaces in the style sheet. Standard CSS element type and
2733 attribute selectors will function adequately in a down-level
2734 client.</li>
2736 <li>In a CSS namespace aware client, the default behavior of
2737 element selectors matching without regard to namespace will
2738 function properly against all elements, since no namespaces are
2739 present. However, the use of specific element type selectors that
2741 will guarantee that selectors will match only XML elements that do
2742 not have a declared namespace. </li>
2744 </ul>
2746 </li>
2748 <li>
2750 <p>The XML document defines a single, default namespace used
2751 throughout the document. No namespace prefixes are used in element
2752 names.</p>
2754 <ul>
2756 <li>In this case, a down-level client will function as if
2757 namespaces were not used in the XML document at all. Standard CSS
2758 element type and attribute selectors will match against all
2759 elements. </li>
2761 </ul>
2763 </li>
2765 <li>
2767 <p>The XML document does <b>not</b> use a default namespace, all
2768 namespace prefixes used are known to the style sheet author, and
2769 there is a direct mapping between namespace prefixes and namespace
2770 URIs. (A given prefix may only be mapped to one namespace URI
2771 throughout the XML document; there may be multiple prefixes mapped
2772 to the same URI).</p>
2774 <ul>
2776 <li>In this case, the down-level client will view and match
2777 element type and attribute selectors based on their fully
2778 qualified name, not the local part as outlined in the <a
2781 to describe the fully qualified names, e.g.
2783 <code><html:h1></code>. Selectors using the qualified name
2784 will only match XML elements that use the same prefix. Other
2785 namespace prefixes used in the XML that are mapped to the same URI
2786 will not match as expected unless additional CSS style rules are
2787 declared for them.</li>
2789 <li>Note that selectors declared in this fashion will
2790 <em>only</em> match in down-level clients. A CSS namespace aware
2791 client will match element type and attribute selectors based on
2792 the name's local part. Selectors declared with the fully
2793 qualified name will not match (unless there is no namespace prefix
2794 in the fully qualified name).</li>
2796 </ul>
2798 </li>
2800 </ol>
2802 <p>In other scenarios: when the namespace prefixes used in the XML are
2803 not known in advance by the style sheet author; or a combination of
2804 elements with no namespace are used in conjunction with elements using
2805 a default namespace; or the same namespace prefix is mapped to
2806 <em>different</em> namespace URIs within the same document, or in
2807 different documents; it is impossible to construct a CSS style sheet
2808 that will function properly against all elements in those documents,
2809 unless, the style sheet is written using a namespace URI syntax (as
2810 outlined in this document or similar) and the document is processed by
2811 a CSS and XML namespace aware client.</p>
2813 <h2><a name=profiling>12. Profiles</a></h2>
2815 <p>Each specification using Selectors must define the subset of W3C
2816 Selectors it allows and excludes, and describe the local meaning of
2817 all the components of that subset.</p>
2819 <p>Non normative examples:
2823 <tbody>
2824 <tr>
2826 <tr>
2827 <th>Specification</th>
2828 <td>CSS level 1</td></tr>
2829 <tr>
2830 <th>Accepts</th>
2831 <td>type selectors<br>class selectors<br>ID selectors<br>:link,
2832 :visited and :active pseudo-classes<br>descendant combinator
2833 <br>::first-line and ::first-letter pseudo-elements</td></tr>
2834 <tr>
2835 <th>Excludes</th>
2836 <td>
2838 <p>universal selector<br>attribute selectors<br>:hover and :focus
2839 pseudo-classes<br>:target pseudo-class<br>:lang() pseudo-class<br>all UI
2840 element states pseudo-classes<br>all structural
2841 pseudo-classes<br>negation pseudo-class<br>all
2842 UI element fragments pseudo-elements<br>::before and ::after
2843 pseudo-elements<br>child combinators<br>sibling combinators
2845 <p>namespaces</td></tr>
2846 <tr>
2847 <th>Extra constraints</th>
2848 <td>only one class selector allowed per sequence of simple
2849 selectors</td></tr></tbody></table><br><br>
2851 <tbody>
2852 <tr>
2854 <tr>
2855 <th>Specification</th>
2856 <td>CSS level 2</td></tr>
2857 <tr>
2858 <th>Accepts</th>
2859 <td>type selectors<br>universal selector<br>attribute presence and
2860 values selectors<br>class selectors<br>ID selectors<br>:link, :visited,
2861 :active, :hover, :focus, :lang() and :first-child pseudo-classes
2862 <br>descendant combinator<br>child combinator<br>adjacent sibling
2863 combinator<br>::first-line and ::first-letter pseudo-elements<br>::before
2864 and ::after pseudo-elements</td></tr>
2865 <tr>
2866 <th>Excludes</th>
2867 <td>
2869 <p>content selectors<br>substring matching attribute
2870 selectors<br>:target pseudo-classes<br>all UI element
2871 states pseudo-classes<br>all structural pseudo-classes other
2872 than :first-child<br>negation pseudo-class<br>all UI element
2873 fragments pseudo-elements<br>general sibling combinators
2875 <p>namespaces</td></tr>
2876 <tr>
2877 <th>Extra constraints</th>
2878 <td>more than one class selector per sequence of simple selectors (CSS1
2879 constraint) allowed</td></tr></tbody></table>
2881 <p>In CSS, selectors express pattern matching rules that determine which style
2882 rules apply to elements in the document tree.
2884 <p>The following selector (CSS level 2) will <b>match</b> all anchors <code>a</code>
2885 with attribute <code>name</code> set inside a section 1 header <code>h1</code>:
2886 <pre>h1 a[name]</pre>
2888 <p>All CSS declarations attached to such a selector are applied to elements
2889 matching it. </div>
2893 <tbody>
2894 <tr>
2896 <tr>
2897 <th>Specification</th>
2898 <td>STTS 3</td>
2899 </tr>
2900 <tr>
2901 <th>Accepts</th>
2902 <td>
2904 <p>type selectors<br>universal selectors<br>attribute selectors<br>class
2905 selectors<br>ID selectors<br>all structural pseudo-classes<br>
2906 all combinators
2908 <p>namespaces</td></tr>
2909 <tr>
2910 <th>Excludes</th>
2911 <td>non-accepted pseudo-classes<br>pseudo-elements<br></td></tr>
2912 <tr>
2913 <th>Extra constraints</th>
2914 <td>some selectors and combinators are not allowed in fragment
2915 descriptions on the right side of STTS declarations.</td></tr></tbody></table>
2916 <form>
2942 </form>
2944 <p>Selectors can be used in STTS 3 in two different
2945 manners:
2946 <ol>
2947 <li>a selection mechanism equivalent to CSS selection mechanism: declarations
2948 attached to a given selector are applied to elements matching that selector,
2949 <li>fragment descriptions that appear on the right side of declarations.
2950 </li></ol></div>
2952 <h2><a name=Conformance></a>13. Conformance and requirements</h2>
2954 <p>This section defines conformance with the present specification only.
2956 <p>The inability of a user agent to implement part of this specification due to
2957 the limitations of a particular device (e.g., non interactive user agents will
2958 probably not implement dynamic pseudo-classes because they make no sense without
2959 interactivity) does not imply non-conformance.
2961 <p>All specifications reusing Selectors must contain a <a
2963 subset of Selectors it accepts or excludes, and describing the constraints
2964 it adds to the current specification.
2966 <p>Invalidity is caused by a parsing error, e.g. an unrecognized token or a token
2967 which is not allowed at the current parsing point.
2969 <p>User agents must observe the rules for handling parsing errors:
2970 <ul>
2971 <li>a simple selector containing an undeclared namespace prefix is invalid</li>
2972 <li>a selector containing an invalid simple selector, an invalid combinator
2973 or an invalid token is invalid. </li>
2974 <li>a group of selectors containing an invalid selector is invalid.</li>
2975 </ul>
2978 errors. (In the case of CSS, the entire rule in which the selector is
2979 used is dropped.)</p>
2981 <!-- Apparently all these references are out of date:
2982 <p>Implementations of this specification must behave as
2984 when parsing selectors and attempting matches. (In particular,
2985 implementations must assume the data is normalized and must not
2986 normalize it.) Normative rules for matching strings are defined in
2989 specification.</p>-->
2991 <h2><a name=Tests></a>14. Tests</h2>
2993 <p>This specification has <a
2995 suite</a> allowing user agents to verify their basic conformance to
2996 the specification. This test suite does not pretend to be exhaustive
2997 and does not cover all possible combined cases of Selectors.</p>
2999 <h2><a name=ACKS></a>15. Acknowledgements</h2>
3001 <p>The CSS working group would like to thank everyone who has sent
3002 comments on this specification over the years.</p>
3004 <p>The working group would like to extend special thanks to Donna
3005 McManus, Justin Baker, Joel Sklar, and Molly Ives Brower who perfermed
3006 the final editorial review.</p>
3008 <h2><a name=references>16. References</a></h2>
3012 <dt>[CSS1]
3013 <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
3016 <dt>[CSS21]
3017 <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
3020 <dt>[CWWW]
3021 <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
3024 <dt>[FLEX]
3025 <dd><a name="refsFLEX"></a> "<cite>Flex: The Lexical Scanner Generator</cite>", Version 2.3.7, ISBN 1882114213
3027 <dt>[HTML4]
3028 <dd><a name="refsHTML4"></a> Dave Ragget, Arnaud Le Hors, Ian Jacobs, editors; "<cite>HTML 4.01 Specification</cite>", W3C Recommendation, 24 December 1999
3031 <dt>[MATH]
3032 <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
3033 <dd>(<code><a href="http://www.w3.org/TR/REC-MathML/">http://www.w3.org/TR/REC-MathML/</a></code>)
3035 <dt>[RFC3066]
3036 <dd><a name="refsRFC3066"></a> H. Alvestrand; "<cite>Tags for the Identification of Languages</cite>", Request for Comments 3066, January 2001
3037 <dd>(<a href="http://www.ietf.org/rfc/rfc3066.txt"><code>http://www.ietf.org/rfc/rfc3066.txt</code></a>)
3039 <dt>[STTS]
3040 <dd><a name=refsSTTS></a> Daniel Glazman; "<cite>Simple Tree Transformation Sheets 3</cite>", Electricité de France, submission to the W3C, 11 November 1998
3041 <dd>(<code><a href="http://www.w3.org/TR/NOTE-STTS3">http://www.w3.org/TR/NOTE-STTS3</a></code>)
3043 <dt>[SVG]
3044 <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
3047 <dt>[UNICODE]</dt>
3049 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>.
3050 <dd>(<code><a href="http://www.unicode.org/versions/">http://www.unicode.org/versions/</a></code>)</dd>
3052 <dt>[XML10]
3053 <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
3056 <dt>[XMLNAMES]
3057 <dd><a name="refsXMLNAMES"></a> Tim Bray, Dave Hollander, Andrew Layman, editors; "<cite>Namespaces in XML</cite>", W3C Recommendation, 14 January 1999
3058 <dd>(<a href="http://www.w3.org/TR/REC-xml-names/"><code>http://www.w3.org/TR/REC-xml-names/</code></a>)
3060 <dt>[YACC]
3061 <dd><a name="refsYACC"></a> S. C. Johnson; "<cite>YACC — Yet another compiler compiler</cite>", Technical Report, Murray Hill, 1975
3063 </dl>
3064 </body>
3065 </html>