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168 <body>
170 <p><a href="http://www.w3.org/"><img height=48 alt=W3C src="http://www.w3.org/Icons/w3c_home" width=72></a>
176 <dl>
178 <dt>This version:
183 <dt>Latest version:
186 http://www.w3.org/TR/css3-selectors</a>
188 <dt>Previous version:
197 <dd class="vcard"><a lang="tr" class="url fn" href="http://www.tantek.com/">Tantek Çelik</a> (Invited Expert)
205 <dd class="vcard"><span class="fn">John Williams</span> (former editor, <span class="company"><a
208 </dl>
219 <a
221 <a
223 <a
225 use</a> rules apply.
229 </div>
234 tree. Selectors have been optimized for use with HTML and XML, and
235 are designed to be usable in performance-critical code.</p>
238 Style Sheets) is a language for describing the rendering of <acronym
241 screen, on paper, in speech, etc. CSS uses Selectors for binding
242 style properties to elements in the document. This document
243 describes extensions to the selectors defined in CSS level 2. These
244 extended selectors will be used by CSS level 3.
250 <p>That is, given an element and a selector, this specification
251 defines whether that element matches the selector.</p>
253 <p>These expressions can also be used, for instance, to select a set
254 of elements, or a single element from a set of elements, by
255 evaluating the expression across all the elements in a
262 <p><em>This section describes the status of this document at the
263 time of its publication. Other documents may supersede this
264 document. A list of current W3C publications and the latest revision
265 of this technical report can be found in the <a
267 http://www.w3.org/TR/.</a></em></p>
275 <p>The CSS Working Group doesn't expect that all implementations of
276 CSS3 will have to implement all selectors. Instead, there will
277 probably be a small number of variants of CSS3, called profiles. For
278 example, it may be that only a profile for interactive user agents
279 will include all of the selectors.</p>
284 document is a revision of the <a
287 implementation feedback received in the past few years. It is
288 expected that this last call will proceed straight to Proposed
289 Recommendation stage since it is believed that interoperability will
290 be demonstrable.</p>
292 <p>All persons are encouraged to review and implement this
293 specification and return comments to the (<a
295 public mailing list <a
298 Members can also send comments directly to the CSS Working
299 Group.
302 <p>This is still a draft document and may be updated, replaced, or
303 obsoleted by other documents at any time. It is inappropriate to
308 The English version of this specification is the only normative
309 version.
317 <ul>
321 </ul>
331 </ul>
333 <ul>
335 </ul>
338 <li class="tocline4"><a href="#attribute-representation">6.3.1. Representation of attributes and attributes values</a>
342 </ul>
352 <ul>
365 </ul>
367 </ul>
368 </li>
369 </ul>
371 <ul>
376 </ul>
383 <li class="tocline4"><a href="#adjacent-sibling-combinators">8.3.1. Adjacent sibling combinator</a>
384 <li class="tocline4"><a href="#general-sibling-combinators">8.3.2. General sibling combinator</a></li>
385 </ul>
386 </li>
387 </ul>
393 </ul>
400 </ul>
402 </div>
408 <p>Some features of this specification are specific to CSS, or have
409 particular limitations or rules specific to CSS. In this
410 specification, these have been described in terms of CSS2.1. <a
415 <p>All of the text of this specification is normative except
416 examples, notes, and sections explicitly marked as
417 non-normative.</p>
423 <p>The main differences between the selectors in CSS2 and those in
424 Selectors are:
426 <ul>
428 <li>the list of basic definitions (selector, group of selectors,
429 simple selector, etc.) has been changed; in particular, what was
430 referred to in CSS2 as a simple selector is now called a sequence
431 of simple selectors, and the term "simple selector" is now used for
432 the components of this sequence</li>
434 <li>an optional namespace component is now allowed in type element
435 selectors, the universal selector and attribute selectors</li>
439 <li>new simple selectors including substring matching attribute
440 selectors, and new pseudo-classes</li>
443 for pseudo-elements</li>
447 <li>profiles to be added to specifications integrating Selectors
448 and defining the set of selectors which is actually supported by
449 each specification</li>
451 <li>Selectors are now a CSS3 Module and an independent
452 specification; other specifications can now refer to this document
453 independently of CSS</li>
457 </ul>
461 <p><em>This section is non-normative, as it merely summarizes the
462 following sections.</em></p>
464 <p>A Selector represents a structure. This structure can be used as a
465 condition (e.g. in a CSS rule) that determines which elements a
466 selector matches in the document tree, or as a flat description of the
467 HTML or XML fragment corresponding to that structure.</p>
469 <p>Selectors may range from simple element names to rich contextual
470 representations.</p>
475 <thead>
476 <tr>
481 <tbody>
482 <tr>
487 selector</a></td>
489 <tr>
495 <tr>
500 selectors</a></td>
502 <tr>
508 selectors</a></td>
510 <tr>
516 selectors</a></td>
518 <tr>
524 selectors</a></td>
526 <tr>
532 selectors</a></td>
534 <tr>
540 selectors</a></td>
542 <tr>
548 selectors</a></td>
550 <tr>
555 pseudo-classes</a></td>
557 <tr>
562 pseudo-classes</a></td>
564 <tr>
567 from the last one</td>
570 pseudo-classes</a></td>
572 <tr>
577 pseudo-classes</a></td>
579 <tr>
582 from the last one</td>
585 pseudo-classes</a></td>
587 <tr>
592 pseudo-classes</a></td>
594 <tr>
599 pseudo-classes</a></td>
601 <tr>
606 pseudo-classes</a></td>
608 <tr>
613 pseudo-classes</a></td>
615 <tr>
620 pseudo-classes</a></td>
622 <tr>
627 pseudo-classes</a></td>
629 <tr>
632 nodes)</td>
635 pseudo-classes</a></td>
637 <tr>
640 which the target is not yet visited (:link) or already visited
641 (:visited)</td>
644 pseudo-classes</a></td>
646 <tr>
651 action pseudo-classes</a></td>
653 <tr>
658 pseudo-class</a></td>
660 <tr>
663 language specifies how language is determined)</td>
666 pseudo-class</a></td>
668 <tr>
671 disabled</td>
674 pseudo-classes</a></td>
676 <tr>
682 pseudo-classes</a></td>
684 <tr>
689 pseudo-element</a></td>
691 <tr>
696 pseudo-element</a></td>
698 <tr>
701 selected/highlighted by the user</td>
704 fragments pseudo-elements</a></td>
706 <tr>
711 pseudo-element</a></td>
713 <tr>
718 pseudo-element</a></td>
720 <tr>
726 selectors</a></td>
728 <tr>
733 selectors</a></td>
735 <tr>
740 pseudo-class</a></td>
742 <tr>
747 combinator</a></td>
749 <tr>
754 combinator</a></td>
756 <tr>
762 <tr>
769 <p>The meaning of each selector is derived from the table above by
771 column.</p>
775 <p>The case sensitivity of document language element names, attribute
776 names, and attribute values in selectors depends on the document
777 language. For example, in HTML, element names are case-insensitive,
778 but in XML, they are case-sensitive.</p>
791 selector or universal selector is allowed in the sequence.</p>
803 sequence of simple selectors.</p>
808 space may appear between a combinator and the simple selectors around
813 never part of white space.</p>
815 <p>The elements of a document tree that are represented by a selector
817 selector consisting of a single sequence of simple selectors
818 represents any element satisfying its requirements. Prepending another
819 sequence of simple selectors and a combinator to a sequence imposes
820 additional matching constraints, so the subjects of a selector are
821 always a subset of the elements represented by the last sequence of
822 simple selectors.</p>
824 <p>An empty selector, containing no sequence of simple selectors and
830 <p>When several selectors share the same declarations, they may be
835 <p>In this example, we condense three rules with identical
836 declarations into one. Thus,</p>
837 <pre>h1 { font-family: sans-serif }
838 h2 { font-family: sans-serif }
839 h3 { font-family: sans-serif }</pre>
842 </div>
845 because all the selectors are valid selectors. If just one of these
846 selectors were invalid, the entire group of selectors would be
847 invalid. This would invalidate the rule for all three heading
848 elements, whereas in the former case only one of the three individual
849 heading rules would be invalidated.</p>
857 element type. A type selector represents an instance of the element
858 type in the document tree.</p>
864 </div>
871 that has been previously declared may be prepended to the element name
875 <p>The namespace component may be left empty to indicate that the
876 selector is only to represent elements with no declared namespace.</p>
878 <p>An asterisk may be used for the namespace prefix, indicating that
879 the selector represents elements in any namespace (including elements
880 with no namespace).</p>
882 <p>Element type selectors that have no namespace component (no
883 namespace separator), represent elements without regard to the
884 element's namespace (equivalent to "<code>*|</code>") unless a default
885 namespace has been declared. If a default namespace has been declared,
886 the selector will represent only elements in the default
887 namespace.</p>
889 <p>A type selector containing a namespace prefix that has not been
891 The mechanism for declaring a namespace prefix is left up to the
892 language implementing Selectors. In CSS, such a mechanism is defined
893 in the General Syntax module.</p>
895 <p>In a namespace-aware client, element type selectors will only match
896 against the <a
898 of the element's <a
901 behaviors in down-level clients.</p>
905 <dl>
909 <dd>elements with name E in any namespace, including those without any
910 declared namespace</dd>
914 <dd>if no default namespace has been specified, this is equivalent to *|E.
915 Otherwise it is equivalent to ns|E where ns is the default namespace.</dd>
916 </dl>
921 <pre>@namespace foo url(http://www.example.com);
922 foo|h1 { color: blue }
923 foo|* { color: yellow }
924 |h1 { color: red }
925 *|h1 { color: green }
926 h1 { color: green }</pre>
931 <p>The second rule will match all elements in the
935 any declared namespace.</p>
938 namespace (including those without any declared namespace).</p>
940 <p>The last rule is equivalent to the fourth rule because no default
941 namespace has been defined.</p>
943 </div>
949 type. It represents any single element in the document tree in any
950 namespace (including those without any declared namespace) if no
951 default namespace has been specified. If a default namespace has been
955 <p>If the universal selector is not the only component of a sequence
960 <ul>
964 </ul>
965 </div>
969 omitted.</p>
973 <p>The universal selector allows an optional namespace component. It
974 is used as follows:</p>
976 <dl>
984 <dd>if no default namespace has been specified, this is equivalent to *|*.
985 Otherwise it is equivalent to ns|* where ns is the default namespace.</dd>
986 </dl>
988 <p>A universal selector containing a namespace prefix that has not
990 selector. The mechanism for declaring a namespace prefix is left up
991 to the language implementing Selectors. In CSS, such a mechanism is
992 defined in the General Syntax module.</p>
997 <p>Selectors allow the representation of an element's attributes. When
998 a selector is used as an expression to match against an element,
999 attribute selectors must be considered to match an element if that
1000 element has an attribute that matches the attribute represented by the
1001 attribute selector.</p>
1004 selectors</a></h4>
1008 <dl>
1011 the attribute.</dd>
1020 spaces).</dd>
1030 </dl>
1032 <p>Attribute values must be identifiers or strings. The
1033 case-sensitivity of attribute names and values in selectors depends on
1034 the document language.</p>
1042 value:</p>
1046 <p>In the following example, the selector represents a
1052 <p>Multiple attribute selectors can be used to represent several
1053 attributes of an element, or several conditions on the same
1062 and "~=". The first selector will represent, for example, the value
1082 <p>Similarly, the following selectors represents a
1086 <pre>DIALOGUE[character=romeo]
1087 DIALOGUE[character=juliet]</pre>
1089 </div>
1092 selectors</h4>
1094 <p>Three additional attribute selectors are provided for matching
1095 substrings in the value of an attribute:</p>
1097 <dl>
1107 </dl>
1109 <p>Attribute values must be identifiers or strings. The
1110 case-sensitivity of attribute names in selectors depends on the
1111 document language.</p>
1116 image:</p>
1124 </div>
1128 <p>Attribute selectors allow an optional namespace component to the
1129 attribute name. A namespace prefix that has been previously declared
1130 may be prepended to the attribute name separated by the namespace
1132 the Namespaces in the XML recommendation, default namespaces do not
1133 apply to attributes, therefore attribute selectors without a namespace
1134 component apply only to attributes that have no declared namespace
1135 (equivalent to "<code>|attr</code>"). An asterisk may be used for the
1136 namespace prefix indicating that the selector is to match all
1137 attribute names without regard to the attribute's namespace.
1139 <p>An attribute selector with an attribute name containing a namespace
1140 prefix that has not been previously declared is an <a
1142 a namespace prefix is left up to the language implementing Selectors.
1143 In CSS, such a mechanism is defined in the General Syntax module.
1148 [foo|att=val] { color: blue }
1149 [*|att] { color: yellow }
1150 [|att] { color: green }
1151 [att] { color: green }</pre>
1153 <p>The first rule will match only elements with the attribute
1157 <p>The second rule will match only elements with the attribute
1159 (including no declared namespace).</p>
1161 <p>The last two rules are equivalent and will match only elements
1163 declared to be in a namespace.</p>
1165 </div>
1169 <p>Attribute selectors represent explicitly set attribute values in
1170 the document tree. Default attribute values may be defined in a DTD or
1171 elsewhere, but cannot always be selected by attribute
1172 selectors. Selectors should be designed so that they work even if the
1173 default values are not included in the document tree.</p>
1182 knowledge of that namespace to treat default attribute values as if
1183 they were present in the document. (For example, an XHTML UA is not
1184 required to use its built-in knowledge of the XHTML DTD.)</p>
1187 choose to ignore external subsets.</p>
1199 <pre>EXAMPLE[notation=decimal] { /*... default property settings ...*/ }
1200 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1203 is set by default, i.e. not set explicitly. To catch all cases, the
1204 attribute selector for the default value must be dropped:</p>
1206 <pre>EXAMPLE { /*... default property settings ...*/ }
1207 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1210 more specific than the tag
1211 selector alone, the style declarations in the second rule will override
1212 those in the first for elements that have a "notation" attribute value
1213 of "octal". Care has to be taken that all property declarations that
1214 are to apply only to the default case are overridden in the non-default
1215 cases' style rules.</p>
1217 </div>
1225 the same meaning. The attribute value must immediately follow the
1228 <p>UAs may apply selectors using the period (.) notation in XML
1229 documents if the UA has namespace-specific knowledge that allows it to
1231 respective namespace. One such example of namespace-specific knowledge
1232 is the prose in the specification for a particular namespace (e.g. SVG
1243 <p>We can assign style information to all elements with
1252 <p>The following assigns style only to H1 elements with
1257 <p>Given these rules, the first H1 instance below would not have
1258 green text, while the second would:</p>
1263 </div>
1273 has been assigned a list of <a
1283 </div>
1286 power to the "class" attribute, authors could conceivably design their
1287 own "document language" based on elements with almost no associated
1288 presentation (such as DIV and SPAN in HTML) and assigning style
1289 information through the "class" attribute. Authors should avoid this
1290 practice since the structural elements of a document language often
1291 have recognized and accepted meanings and author-defined classes may
1292 not.</p>
1295 class attributes, their values must be concatenated with spaces
1296 between the values before searching for the class. As of this time the
1297 working group is not aware of any manner in which this situation can
1298 be reached, however, so this behavior is explicitly non-normative in
1299 this specification.</p>
1303 <p>Document languages may contain attributes that are declared to be
1304 of type ID. What makes attributes of type ID special is that no two
1305 such attributes can have the same value in a document, regardless of
1306 the type of the elements that carry them; whatever the document
1307 language, an ID typed attribute can be used to uniquely identify its
1308 element. In HTML all ID attributes are named "id"; XML applications
1309 may name ID attributes differently, but the same restriction
1310 applies.</p>
1312 <p>An ID-typed attribute of a document language allows authors to
1313 assign an identifier to one element instance in the document tree. W3C
1314 ID selectors represent an element instance based on its identifier. An
1317 identifier.</p>
1319 <p>Selectors does not specify how a UA knows the ID-typed attribute of
1320 an element. The UA may, e.g., read a document's DTD, have the
1321 information hard-coded or ask the user.
1328 <p>The following ID selector represents any element whose ID-typed
1331 <p>The following selector represents any element whose ID-typed
1334 </div>
1338 contains an element's IDs is contained in a DTD or a schema. When
1339 parsing XML, UAs do not always read the DTD, and thus may not know
1340 what the ID of an element is (though a UA may have namespace-specific
1341 knowledge that allows it to determine which attribute is the ID
1342 attribute for that namespace). If a style sheet designer knows or
1343 suspects that a UA may not know what the ID of an element is, he
1344 should use normal attribute selectors instead:
1348 <p>If an element has multiple ID attributes, all of them must be
1349 treated as IDs for that element for the purposes of the ID
1350 selector. Such a situation could be reached using mixtures of xml:id,
1351 DOM3 Core, XML DTDs, and namespace-specific knowledge.</p>
1355 <p>The pseudo-class concept is introduced to permit selection based on
1356 information that lies outside of the document tree or that cannot be
1357 expressed using the other simple selectors.</p>
1361 optionally by a value between parentheses.</p>
1363 <p>Pseudo-classes are allowed in all sequences of simple selectors
1364 contained in a selector. Pseudo-classes are allowed anywhere in
1365 sequences of simple selectors, after the leading type selector or
1366 universal selector (possibly omitted). Pseudo-class names are
1367 case-insensitive. Some pseudo-classes are mutually exclusive, while
1368 others can be applied simultaneously to the same
1369 element. Pseudo-classes may be dynamic, in the sense that an element
1370 may acquire or lose a pseudo-class while a user interacts with the
1371 document.</p>
1376 <p>Dynamic pseudo-classes classify elements on characteristics other
1377 than their name, attributes, or content, in principle characteristics
1378 that cannot be deduced from the document tree.</p>
1380 <p>Dynamic pseudo-classes do not appear in the document source or
1381 document tree.</p>
1386 <p>User agents commonly display unvisited links differently from
1387 previously visited ones. Selectors
1391 <ul>
1393 not yet been visited.</li>
1395 been visited by the user. </li>
1396 </ul>
1398 <p>After some amount of time, user agents may choose to return a
1399 visited link to the (unvisited) ':link' state.</p>
1407 <p>The following selector represents links carrying class
1412 </div>
1415 authors to abuse the :link and :visited pseudo-classes to determine
1416 which sites a user has visited without the user's consent.
1418 <p>UAs may therefore treat all links as unvisited links, or implement
1419 other measures to preserve the user's privacy while rendering visited
1420 and unvisited links differently.</p>
1423 :hover, :active, and :focus</a></h5>
1425 <p>Interactive user agents sometimes change the rendering in response
1426 to user actions. Selectors provides
1427 three pseudo-classes for the selection of an element the user is
1428 acting on.</p>
1430 <ul>
1433 designates an element with a pointing device, but does not activate
1434 it. For example, a visual user agent could apply this pseudo-class
1435 when the cursor (mouse pointer) hovers over a box generated by the
1436 element. User agents not that do not support <a
1438 media</a> do not have to support this pseudo-class. Some conforming
1439 user agents that support <a
1441 media</a> may not be able to support this pseudo-class (e.g., a pen
1442 device that does not detect hovering).</li>
1445 is being activated by the user. For example, between the times the
1446 user presses the mouse button and releases it.</li>
1449 has the focus (accepts keyboard or mouse events, or other forms of
1450 input). </li>
1452 </ul>
1454 <p>There may be document language or implementation specific limits on
1458 <p>These pseudo-classes are not mutually exclusive. An element may
1459 match several pseudo-classes at the same time.</p>
1461 <p>Selectors doesn't define if the parent of an element that is
1462 ':active' or ':hover' is also in that state.</p>
1466 <pre>a:link /* unvisited links */
1467 a:visited /* visited links */
1468 a:hover /* user hovers */
1469 a:active /* active links */</pre>
1471 <pre>a:focus
1472 a:focus:hover</pre>
1474 the pseudo-class :focus and in the pseudo-class :hover.</p>
1475 </div>
1478 and ':active' (or ':link' and ':active').</p>
1482 <p>Some URIs refer to a location within a resource. This kind of URI
1484 identifier (called the fragment identifier).</p>
1486 <p>URIs with fragment identifiers link to a certain element within the
1487 document, known as the target element. For instance, here is a URI
1489 document:</p>
1494 pseudo-class. If the document's URI has no fragment identifier, then
1495 the document has no target element.</p>
1502 URI.</p>
1503 </div>
1508 target element red and place an image before it, if there is one:</p>
1509 <pre>*:target { color : red }
1510 *:target::before { content : url(target.png) }</pre>
1511 </div>
1515 <p>If the document language specifies how the human language of an
1516 element is determined, it is possible to write selectors that
1517 represent an element based on its language. For example, in HTML <a
1520 element, and possibly by information from the protocol (such as HTTP
1522 there may be other document language-specific methods for determining
1523 the language.</p>
1526 is in language C. Whether an element is represented by a
1528 being either equal to, or a hyphen-separated substring of, the
1529 element's language value, in the same way as if performed by the <a
1531 selectors. The identifier C does not have to be a valid language
1532 name.</p>
1546 <p>The two following selectors represent an HTML document that is in
1547 Belgian, French, or German. The two next selectors represent
1549 or German.</p>
1550 <pre>html:lang(fr-be)
1551 html:lang(de)
1552 :lang(fr-be) > q
1554 </div>
1561 the look of user interface elements that are enabled — which the
1562 user can select or activate in some fashion (e.g. clicking on a button
1563 with a mouse). There is a need for such a pseudo-class because there
1564 is no way to programmatically specify the default appearance of say,
1566 would look like when it was disabled.</p>
1569 author to specify precisely how a disabled or inactive user interface
1570 element should look.</p>
1572 <p>Most elements will be neither enabled nor disabled. An element is
1573 enabled if the user can either activate it or transfer the focus to
1574 it. An element is disabled if it could be enabled, but the user cannot
1575 presently activate it or transfer focus to it.</p>
1580 <p>Radio and checkbox elements can be toggled by the user. Some menu
1581 items are "checked" when the user selects them. When such elements are
1585 attributes as described in <a
1590 in nature, and is altered by user action, since it can also be based
1599 <p>Radio and checkbox elements can be toggled by the user, but are
1600 sometimes in an indeterminate state, neither checked nor unchecked.
1601 This can be due to an element attribute, or DOM manipulation.</p>
1603 <p>A future version of this specification may introduce an
1605 <!--While the <code>:indeterminate</code> pseudo-class is dynamic in
1606 nature, and is altered by user action, since it can also be based on
1607 the presence of an element attribute, it applies to all media.</p>
1609 <p>Components of a radio-group initialized with no pre-selected choice
1612 </div>
1618 pseudo-classes</dfn> to permit selection based on extra information that lies in
1619 the document tree but cannot be represented by other simple selectors or
1620 combinators.
1622 <p>Note that standalone pieces of PCDATA (text nodes in the DOM) are
1623 not counted when calculating the position of an element in the list of
1624 children of its parent. When calculating the position of an element in
1625 the list of children of its parent, the index numbering starts at 1.
1631 the root of the document. In HTML 4, this is always the
1637 <p>The
1639 pseudo-class notation represents an element that has
1645 each. For example, this allows the selectors to address every other
1646 row in a table, and could be used to alternate the color
1649 integers. The index of the first child of an element is 1.
1660 tr:nth-child(odd) /* same */
1661 tr:nth-child(2n) /* represents every even row of an HTML table */
1662 tr:nth-child(even) /* same */
1664 /* Alternate paragraph colours in CSS */
1669 </div>
1674 included, so the syntax simplifies to
1682 </div>
1690 bar:nth-child(n+0) /* same */
1691 bar:nth-child(n) /* same */
1693 </div>
1702 </div>
1705 pseudo-class represents no element in the document tree.</p>
1710 tree.</p>
1715 </div>
1718 expression must be removed (it is effectively replaced by the "-"
1726 </div>
1732 pseudo-class notation represents an element that has
1738 as arguments.
1745 foo:nth-last-child(odd) /* represents all odd foo elements in their parent element,
1746 counting from the last one */</pre>
1747 </div>
1753 pseudo-class notation represents an element that has
1758 of that type after all the children of that type have been split into
1760 for the syntax of its argument. It also accepts the
1769 </div>
1775 pseudo-class notation represents an element that has
1787 following selector:</p>
1790 selector ends up being just as long:</p>
1792 </div>
1798 represents an element that is the first child of some other element.
1812 fragment:
1820 a:first-child /* Same (assuming a is not the root element) */</pre>
1821 </div>
1826 represents an element that is the last child of some other element.
1833 </div>
1838 represents an element that is the first sibling of its type in the list of
1839 children of its parent element.
1843 <p>The following selector represents a definition title
1846 its parent element.</p>
1849 elements in the following example but not for the third one:</p>
1861 </div>
1867 the last sibling of its type in the list of children of its parent
1868 element.</p>
1872 <p>The following selector represents the last data cell
1875 </div>
1879 <p>Represents an element that has a parent element and whose parent
1880 element has no other element children. Same as
1883 specificity.</p>
1887 <p>Represents an element that has a parent element and whose parent
1888 element has no other element children with the same element name. Same
1891 specificity.</p>
1897 no children at all. In terms of the DOM, only element nodes and text
1898 nodes (including CDATA nodes and entity references) whose data has a
1899 non-zero length must be considered as affecting emptiness; comments,
1900 PIs, and other nodes must not affect whether an element is considered
1901 empty or not.</p>
1908 following fragments:</p>
1912 </div>
1914 <h4><a name=content-selectors>6.6.6. Blank</a></h4> <!-- It's the Return of Appendix H!!! Run away! -->
1917 <!-- (used to be :contains()) -->
1923 selector</a> (excluding the negation pseudo-class itself and
1924 pseudo-elements) as an argument. It represents an element that is not
1925 represented by the argument.
1927 <!-- pseudo-elements are not simple selectors, so the above paragraph
1928 may be a bit confusing -->
1933 elements in an HTML document that are not disabled.</p>
1936 elements.</p>
1938 <p>The following group of selectors represents all HTML elements
1939 except links.</p>
1941 </div>
1943 <p>Default namespace declarations do not affect the argument of the
1944 negation pseudo-class unless the argument is a universal selector or a
1945 type selector.</p>
1949 <p>Assuming that the default namespace is bound to
1950 "http://example.com/", the following selector represents all
1951 elements that are not in that namespace:</p>
1953 <p>The following CSS selector matches any element being hovered,
1954 regardless of its namespace. In particular, it is not limited to
1955 only matching elements in the default namespace that are not being
1956 hovered, and elements not in the default namespace don't match the
1959 </div>
1965 specificity.</p>
1969 <p>Pseudo-elements create abstractions about the document tree beyond
1970 those specified by the document language. For instance, document
1971 languages do not offer mechanisms to access the first letter or first
1972 line of an element's content. Pseudo-elements allow designers to refer
1973 to this otherwise inaccessible information. Pseudo-elements may also
1974 provide designers a way to refer to content that does not exist in the
1977 content).</p>
1980 by the name of the pseudo-element.</p>
1983 in order to establish a discrimination between pseudo-classes and
1984 pseudo-elements. For compatibility with existing style sheets, user
1985 agents must also accept the previous one-colon notation for
1991 <p>Only one pseudo-element may appear per selector, and if present it
1992 must appear after the sequence of simple selectors that represents the
1994 future version of this specification may allow multiple
1995 pesudo-elements per selector.</span></p>
2000 of the first formatted line of an element.
2007 </div>
2010 HTML element. It does match a pseudo-element that conforming user
2011 agents will insert at the beginning of every paragraph.</p>
2013 <p>Note that the length of the first line depends on a number of
2014 factors, including the width of the page, the font size, etc. Thus,
2015 an ordinary HTML paragraph such as:</p>
2017 <pre>
2019 paragraph that will be broken into several
2020 lines. The first line will be identified
2021 by a fictional tag sequence. The other lines
2022 will be treated as ordinary lines in the
2024 </pre>
2026 <p>the lines of which happen to be broken as follows:
2028 <pre>
2029 THIS IS A SOMEWHAT LONG HTML PARAGRAPH THAT
2030 will be broken into several lines. The first
2031 line will be identified by a fictional tag
2032 sequence. The other lines will be treated as
2033 ordinary lines in the paragraph.
2034 </pre>
2038 fictional tag sequence helps to show how properties are inherited.</p>
2040 <pre>
2043 lines. The first line will be identified
2044 by a fictional tag sequence. The other lines
2045 will be treated as ordinary lines in the
2047 </pre>
2049 <p>If a pseudo-element breaks up a real element, the desired effect
2050 can often be described by a fictional tag sequence that closes and
2051 then re-opens the element. Thus, if we mark up the previous paragraph
2054 <pre>
2056 paragraph that will be broken into several
2058 by a fictional tag sequence. The other lines
2059 will be treated as ordinary lines in the
2061 </pre>
2063 <p>the user agent could simulate start and end tags for
2067 <pre>
2069 somewhat long HTML
2070 paragraph that will <b></SPAN></b></P::first-line><b><SPAN class="test"></b> be
2071 broken into several
2073 by a fictional tag sequence. The other lines
2074 will be treated as ordinary lines in the
2076 </pre>
2079 attached to a block-level element, an inline-block, a table-caption,
2080 or a table-cell.</p>
2083 element may occur inside a
2084 block-level descendant in the same flow (i.e., a block-level
2085 descendant that is not positioned and not a float). E.g., the first
2090 <p>The first line of a table-cell or inline-block cannot be the first
2101 <p>A UA should act as if the fictional start tags of the
2103 innermost enclosing block-level element. (Since CSS1 and CSS2 were
2104 silent on this case, authors should not rely on this behavior.) Here
2105 is an example. The fictional tag sequence for</p>
2107 <pre>
2112 </pre>
2116 <pre>
2118 <P><DIV::first-line><P::first-line>First paragraph</P::first-line></DIV::first-line></P>
2121 </pre>
2124 inline-level element, but with certain restrictions. In CSS, the
2126 pseudo-element: font properties, color property, background
2127 properties, 'word-spacing', 'letter-spacing', 'text-decoration',
2128 'vertical-align', 'text-transform', 'line-height'. UAs may apply other
2129 properties as well.</p>
2135 letter of the first line of a block, if it is not preceded by any
2136 other content (such as images or inline tables) on its line. The
2138 caps", which are common typographical effects. This type of initial
2139 letter is similar to an inline-level element if its 'float' property
2140 is 'none'; otherwise, it is similar to a floated element.</p>
2143 pseudo-elements: font properties, 'text-decoration', 'text-transform',
2144 'letter-spacing', 'word-spacing' (when appropriate), 'line-height',
2145 'float', 'vertical-align' (only if 'float' is 'none'), margin
2146 properties, padding properties, border properties, color property,
2147 background properties. UAs may apply other properties as well. To
2148 allow UAs to render a typographically correct drop cap or initial cap,
2149 the UA may choose a line-height, width and height based on the shape
2150 of the letter, unlike for normal elements.</p>
2154 <p>This example shows a possible rendering of an initial cap. Note
2156 pseudo-element is 1.1, but the UA in this example has computed the
2157 height of the first letter differently, so that it doesn't cause any
2158 unnecessary space between the first two lines. Also note that the
2161 <pre>
2162 p { line-height: 1.1 }
2163 p::first-letter { font-size: 3em; font-weight: normal }
2164 span { font-weight: bold }
2165 ...
2169 En dagelix geschrey de bange stad ontzet.
2170 </pre>
2173 </div>
2174 </div>
2179 <pre>
2186 P::first-letter { font-size: 200%; font-weight: bold; float: left }
2187 SPAN { text-transform: uppercase }
2195 </pre>
2200 <P><img src="first-letter.gif" alt="Image illustrating the combined effect of the ::first-letter and ::first-line pseudo-elements"></p>
2201 </div>
2206 <pre>
2210 T
2213 few words of an article in the Economist.
2215 </pre>
2218 the content (i.e., the initial character), while the ::first-line
2219 pseudo-element start tag is inserted right after the start tag of the
2220 block element.</p> </div>
2222 <p>In order to achieve traditional drop caps formatting, user agents
2223 may approximate font sizes, for example to align baselines. Also, the
2224 glyph outline may be taken into account when formatting.</p>
2228 punctuation classes), that precedes or follows the first letter should
2234 </div>
2241 block, list-item, table-cell, table-caption, and inline-block
2243 may allow this pesudo-element to apply to more element
2244 types.</span></p>
2247 such elements that contain text, or that have a descendant in the same
2248 flow that contains text. A UA should act as if the fictional start tag
2249 of the ::first-letter pseudo-element is just before the first text of
2250 the element, even if that first text is in a descendant.</p>
2254 <p>The fictional tag sequence for this HTMLfragment:
2257 <p>is:
2260 </div>
2262 <p>The first letter of a table-cell or inline-block cannot be the
2275 <p>In CSS, if an element is a list item ('display: list-item'), the
2277 principal box after the marker. UAs may ignore
2287 </div>
2289 <p>Some languages may have specific rules about how to treat certain
2290 letter combinations. In Dutch, for example, if the letter combination
2291 "ij" appears at the beginning of a word, both letters should be
2294 <p>If the letters that would form the ::first-letter are not in the
2296 may create a ::first-letter pseudo-element from one of the elements,
2297 both elements, or simply not create a pseudo-element.</p>
2299 <p>Similarly, if the first letter(s) of the block are not at the start
2300 of the line (for example due to bidirectional reordering), then the UA
2301 need not create the pseudo-element(s).
2306 how overlapping pseudo-elements may interact. The first letter of
2307 each P element will be green with a font size of '24pt'. The rest of
2308 the first formatted line will be 'blue' while the rest of the
2309 paragraph will be 'red'.</p>
2312 p::first-letter { color: green; font-size: 200% }
2313 p::first-line { color: blue }
2324 S
2327 ends up on two lines
2334 </div>
2340 of a document that has been highlighted by the user. This also
2341 applies, for example, to selected text within an editable text
2342 field. This pseudo-element should not be confused with the <code><a
2347 nature, and is altered by user action, it is reasonable to expect that
2348 when a UA re-renders to a static medium (such as a printed page, see
2350 dynamic medium (like screen), the UA may wish to transfer the current
2352 appropriate formatting and rendering take effect as well. This is not
2354 pseudo-element for static media.
2357 pseudo-elements: color, background, cursor (optional), outline
2358 (optional). The computed value of the 'background-image' property on
2365 can be used to describe generated content before or after an element's
2372 element including the inserted text.</p>
2378 <p>At times, authors may want selectors to describe an element that is
2379 the descendant of another element in the document tree (e.g., "an
2380 <code>EM</code> element that is contained within an <code>H1</code>
2381 element"). Descendant combinators express such a relationship. A
2383 separates two sequences of simple selectors. A selector of the form
2393 description of the following fragment:</p>
2400 either side of the "*" is not part of the universal selector; the
2401 whitespace is a combinator indicating that the DIV must be the
2402 ancestor of some element, and that that element must be an ancestor
2403 of the P.</p>
2404 <p>The following selector, which combines descendant combinators and
2409 </div>
2414 between two elements. A child combinator is made of the
2416 separates two sequences of simple selectors.
2424 <p>The following example combines descendant combinators and child
2425 combinators.</p>
2432 </div>
2434 <p>For information on selecting the first child of an element, please
2435 see the section on the <code><a
2437 above.</p>
2441 <p>There are two different sibling combinators: the adjacent sibling
2442 combinator and the general sibling combinator. In both cases,
2443 non-element nodes (e.g. text between elements) are ignored when
2444 considering adjacency of elements.</p>
2450 sequences of simple selectors. The elements represented by the two
2451 sequences share the same parent in the document tree and the element
2452 represented by the first sequence immediately precedes the element
2453 represented by the second one.</p>
2460 <p>The following selector is conceptually similar to the one in the
2461 previous example, except that it adds an attribute selector — it
2465 </div>
2472 simple selectors. The elements represented by the two sequences share
2473 the same parent in the document tree and the element represented by
2474 the first sequence precedes (not necessarily immediately) the element
2475 represented by the second one.</p>
2481 is a correct and valid, but partial, description of:</p>
2485 </div>
2491 <ul>
2493 <li>count the number of class selectors, attributes selectors, and pseudo-classes in the selector (= b)</li>
2496 </ul>
2499 are counted like any other, but the negation itself does not count as
2500 a pseudo-class.</p>
2502 <p>Concatenating the three numbers a-b-c (in a number system with a
2503 large base) gives the specificity.</p>
2516 </pre>
2517 </div>
2527 <p>The grammar below defines the syntax of Selectors. It is globally
2529 it directly, since it doesn't express the parsing conventions). The
2530 format of the productions is optimized for human consumption and some
2532 are used:</p>
2534 <ul>
2540 </ul>
2544 <pre>selectors_group
2545 : selector [ COMMA S* selector ]*
2546 ;
2548 selector
2549 : simple_selector_sequence [ combinator simple_selector_sequence ]*
2550 ;
2552 combinator
2553 /* combinators can be surrounded by white space */
2554 : PLUS S* | GREATER S* | TILDE S* | S+
2555 ;
2557 simple_selector_sequence
2558 : [ type_selector | universal ]
2559 [ HASH | class | attrib | pseudo | negation ]*
2560 | [ HASH | class | attrib | pseudo | negation ]+
2561 ;
2563 type_selector
2564 : [ namespace_prefix ]? element_name
2565 ;
2567 namespace_prefix
2568 : [ IDENT | '*' ]? '|'
2569 ;
2571 element_name
2572 : IDENT
2573 ;
2575 universal
2576 : [ namespace_prefix ]? '*'
2577 ;
2579 class
2580 : '.' IDENT
2581 ;
2583 attrib
2584 : '[' S* [ namespace_prefix ]? IDENT S*
2585 [ [ PREFIXMATCH |
2586 SUFFIXMATCH |
2587 SUBSTRINGMATCH |
2588 '=' |
2589 INCLUDES |
2590 DASHMATCH ] S* [ IDENT | STRING ] S*
2591 ]? ']'
2592 ;
2594 pseudo
2595 /* '::' starts a pseudo-element, ':' a pseudo-class */
2596 /* Exceptions: :first-line, :first-letter, :before and :after. */
2597 /* Note that pseudo-elements are restricted to one per selector and */
2598 /* occur only in the last simple_selector_sequence. */
2599 : ':' ':'? [ IDENT | functional_pseudo ]
2600 ;
2602 functional_pseudo
2603 : FUNCTION S* expression ')'
2604 ;
2606 expression
2607 /* In CSS3, the expressions are identifiers, strings, */
2608 /* or of the form "an+b" */
2609 : [ [ PLUS | '-' | DIMENSION | NUMBER | STRING | IDENT ] S* ]+
2610 ;
2612 negation
2613 : NOT S* negation_arg S* ')'
2614 ;
2616 negation_arg
2617 : type_selector | universal | HASH | class | attrib | pseudo
2618 ;</pre>
2625 case-insensitive.</p>
2628 number that current versions of Flex can deal with (decimal 255). They
2633 <pre>%option case-insensitive
2635 ident [-]?{nmstart}{nmchar}*
2636 name {nmchar}+
2637 nmstart [_a-z]|{nonascii}|{escape}
2640 escape {unicode}|\\[^\n\r\f0-9a-f]
2641 nmchar [_a-z0-9-]|{nonascii}|{escape}
2643 string {string1}|{string2}
2645 string2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*\'
2646 invalid {invalid1}|{invalid2}
2648 invalid2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*
2649 nl \n|\r\n|\r|\f
2650 w [ \t\r\n\f]*
2652 %%
2654 [ \t\r\n\f]+ return S;
2661 {ident} return IDENT;
2662 {string} return STRING;
2664 {num} return NUMBER;
2671 @{ident} return ATKEYWORD;
2672 {invalid} return INVALID;
2673 {num}% return PERCENTAGE;
2674 {num}{ident} return DIMENSION;
2680 U\+[0-9a-f?]{1,6}(-[0-9a-f]{1,6})? return UNICODE_RANGE;
2682 \/\*[^*]*\*+([^/*][^*]*\*+)*\/ /* ignore comments */
2684 . return *yytext;</pre>
2688 <h2><a name=downlevel>11. Namespaces and down-level clients</a></h2>
2690 <p>An important issue is the interaction of CSS selectors with XML
2691 documents in web clients that were produced prior to this
2692 document. Unfortunately, due to the fact that namespaces must be
2693 matched based on the URI which identifies the namespace, not the
2694 namespace prefix, some mechanism is required to identify namespaces in
2695 CSS by their URI as well. Without such a mechanism, it is impossible
2696 to construct a CSS style sheet which will properly match selectors in
2697 all cases against a random set of XML documents. However, given
2698 complete knowledge of the XML document to which a style sheet is to be
2699 applied, and a limited use of namespaces within the XML document, it
2700 is possible to construct a style sheet in which selectors would match
2701 elements and attributes correctly.</p>
2703 <p>It should be noted that a down-level CSS client will (if it
2704 properly conforms to CSS forward compatible parsing rules) ignore all
2705 <code>@namespace</code> at-rules, as well as all style rules that make
2706 use of namespace qualified element type or attribute selectors. The
2707 syntax of delimiting namespace prefixes in CSS was deliberately chosen
2708 so that down-level CSS clients would ignore the style rules rather
2709 than possibly match them incorrectly.</p>
2711 <p>The use of default namespaces in CSS makes it possible to write
2712 element type selectors that will function in both namespace aware CSS
2713 clients as well as down-level clients. It should be noted that
2714 down-level clients may incorrectly match selectors against XML
2715 elements in other namespaces.</p>
2717 <p>The following are scenarios and examples in which it is possible to
2718 construct style sheets which would function properly in web clients
2719 that do not implement this proposal.</p>
2721 <ol>
2722 <li>
2724 <p>The XML document does not use namespaces.</p>
2726 <ul>
2728 <li>In this case, it is obviously not necessary to declare or use
2729 namespaces in the style sheet. Standard CSS element type and
2730 attribute selectors will function adequately in a down-level
2731 client.</li>
2733 <li>In a CSS namespace aware client, the default behavior of
2734 element selectors matching without regard to namespace will
2735 function properly against all elements, since no namespaces are
2736 present. However, the use of specific element type selectors that
2738 will guarantee that selectors will match only XML elements that do
2739 not have a declared namespace. </li>
2741 </ul>
2743 </li>
2745 <li>
2747 <p>The XML document defines a single, default namespace used
2748 throughout the document. No namespace prefixes are used in element
2749 names.</p>
2751 <ul>
2753 <li>In this case, a down-level client will function as if
2754 namespaces were not used in the XML document at all. Standard CSS
2755 element type and attribute selectors will match against all
2756 elements. </li>
2758 </ul>
2760 </li>
2762 <li>
2764 <p>The XML document does <b>not</b> use a default namespace, all
2765 namespace prefixes used are known to the style sheet author, and
2766 there is a direct mapping between namespace prefixes and namespace
2767 URIs. (A given prefix may only be mapped to one namespace URI
2768 throughout the XML document; there may be multiple prefixes mapped
2769 to the same URI).</p>
2771 <ul>
2773 <li>In this case, the down-level client will view and match
2774 element type and attribute selectors based on their fully
2775 qualified name, not the local part as outlined in the <a
2778 to describe the fully qualified names, e.g.
2780 <code><html:h1></code>. Selectors using the qualified name
2781 will only match XML elements that use the same prefix. Other
2782 namespace prefixes used in the XML that are mapped to the same URI
2783 will not match as expected unless additional CSS style rules are
2784 declared for them.</li>
2786 <li>Note that selectors declared in this fashion will
2787 <em>only</em> match in down-level clients. A CSS namespace aware
2788 client will match element type and attribute selectors based on
2789 the name's local part. Selectors declared with the fully
2790 qualified name will not match (unless there is no namespace prefix
2791 in the fully qualified name).</li>
2793 </ul>
2795 </li>
2797 </ol>
2799 <p>In other scenarios: when the namespace prefixes used in the XML are
2800 not known in advance by the style sheet author; or a combination of
2801 elements with no namespace are used in conjunction with elements using
2802 a default namespace; or the same namespace prefix is mapped to
2803 <em>different</em> namespace URIs within the same document, or in
2804 different documents; it is impossible to construct a CSS style sheet
2805 that will function properly against all elements in those documents,
2806 unless, the style sheet is written using a namespace URI syntax (as
2807 outlined in this document or similar) and the document is processed by
2808 a CSS and XML namespace aware client.</p>
2810 <h2><a name=profiling>12. Profiles</a></h2>
2812 <p>Each specification using Selectors must define the subset of W3C
2813 Selectors it allows and excludes, and describe the local meaning of
2814 all the components of that subset.</p>
2816 <p>Non normative examples:
2820 <tbody>
2821 <tr>
2823 <tr>
2824 <th>Specification</th>
2825 <td>CSS level 1</td></tr>
2826 <tr>
2827 <th>Accepts</th>
2828 <td>type selectors<br>class selectors<br>ID selectors<br>:link,
2829 :visited and :active pseudo-classes<br>descendant combinator
2830 <br>::first-line and ::first-letter pseudo-elements</td></tr>
2831 <tr>
2832 <th>Excludes</th>
2833 <td>
2835 <p>universal selector<br>attribute selectors<br>:hover and :focus
2836 pseudo-classes<br>:target pseudo-class<br>:lang() pseudo-class<br>all UI
2837 element states pseudo-classes<br>all structural
2838 pseudo-classes<br>negation pseudo-class<br>all
2839 UI element fragments pseudo-elements<br>::before and ::after
2840 pseudo-elements<br>child combinators<br>sibling combinators
2842 <p>namespaces</td></tr>
2843 <tr>
2844 <th>Extra constraints</th>
2845 <td>only one class selector allowed per sequence of simple
2846 selectors</td></tr></tbody></table><br><br>
2848 <tbody>
2849 <tr>
2851 <tr>
2852 <th>Specification</th>
2853 <td>CSS level 2</td></tr>
2854 <tr>
2855 <th>Accepts</th>
2856 <td>type selectors<br>universal selector<br>attribute presence and
2857 values selectors<br>class selectors<br>ID selectors<br>:link, :visited,
2858 :active, :hover, :focus, :lang() and :first-child pseudo-classes
2859 <br>descendant combinator<br>child combinator<br>adjacent sibling
2860 combinator<br>::first-line and ::first-letter pseudo-elements<br>::before
2861 and ::after pseudo-elements</td></tr>
2862 <tr>
2863 <th>Excludes</th>
2864 <td>
2866 <p>content selectors<br>substring matching attribute
2867 selectors<br>:target pseudo-classes<br>all UI element
2868 states pseudo-classes<br>all structural pseudo-classes other
2869 than :first-child<br>negation pseudo-class<br>all UI element
2870 fragments pseudo-elements<br>general sibling combinators
2872 <p>namespaces</td></tr>
2873 <tr>
2874 <th>Extra constraints</th>
2875 <td>more than one class selector per sequence of simple selectors (CSS1
2876 constraint) allowed</td></tr></tbody></table>
2878 <p>In CSS, selectors express pattern matching rules that determine which style
2879 rules apply to elements in the document tree.
2881 <p>The following selector (CSS level 2) will <b>match</b> all anchors <code>a</code>
2882 with attribute <code>name</code> set inside a section 1 header <code>h1</code>:
2883 <pre>h1 a[name]</pre>
2885 <p>All CSS declarations attached to such a selector are applied to elements
2886 matching it. </div>
2890 <tbody>
2891 <tr>
2893 <tr>
2894 <th>Specification</th>
2895 <td>STTS 3</td>
2896 </tr>
2897 <tr>
2898 <th>Accepts</th>
2899 <td>
2901 <p>type selectors<br>universal selectors<br>attribute selectors<br>class
2902 selectors<br>ID selectors<br>all structural pseudo-classes<br>
2903 all combinators
2905 <p>namespaces</td></tr>
2906 <tr>
2907 <th>Excludes</th>
2908 <td>non-accepted pseudo-classes<br>pseudo-elements<br></td></tr>
2909 <tr>
2910 <th>Extra constraints</th>
2911 <td>some selectors and combinators are not allowed in fragment
2912 descriptions on the right side of STTS declarations.</td></tr></tbody></table>
2913 <form>
2939 </form>
2941 <p>Selectors can be used in STTS 3 in two different
2942 manners:
2943 <ol>
2944 <li>a selection mechanism equivalent to CSS selection mechanism: declarations
2945 attached to a given selector are applied to elements matching that selector,
2946 <li>fragment descriptions that appear on the right side of declarations.
2947 </li></ol></div>
2949 <h2><a name=Conformance></a>13. Conformance and requirements</h2>
2951 <p>This section defines conformance with the present specification only.
2953 <p>The inability of a user agent to implement part of this specification due to
2954 the limitations of a particular device (e.g., non interactive user agents will
2955 probably not implement dynamic pseudo-classes because they make no sense without
2956 interactivity) does not imply non-conformance.
2958 <p>All specifications reusing Selectors must contain a <a
2960 subset of Selectors it accepts or excludes, and describing the constraints
2961 it adds to the current specification.
2963 <p>Invalidity is caused by a parsing error, e.g. an unrecognized token or a token
2964 which is not allowed at the current parsing point.
2966 <p>User agents must observe the rules for handling parsing errors:
2967 <ul>
2968 <li>a simple selector containing an undeclared namespace prefix is invalid</li>
2969 <li>a selector containing an invalid simple selector, an invalid combinator
2970 or an invalid token is invalid. </li>
2971 <li>a group of selectors containing an invalid selector is invalid.</li>
2972 </ul>
2975 errors. (In the case of CSS, the entire rule in which the selector is
2976 used is dropped.)</p>
2978 <!-- Apparently all these references are out of date:
2979 <p>Implementations of this specification must behave as
2981 when parsing selectors and attempting matches. (In particular,
2982 implementations must assume the data is normalized and must not
2983 normalize it.) Normative rules for matching strings are defined in
2986 specification.</p>-->
2988 <h2><a name=Tests></a>14. Tests</h2>
2990 <p>This specification has <a
2992 suite</a> allowing user agents to verify their basic conformance to
2993 the specification. This test suite does not pretend to be exhaustive
2994 and does not cover all possible combined cases of Selectors.</p>
2996 <h2><a name=ACKS></a>15. Acknowledgements</h2>
2998 <p>The CSS working group would like to thank everyone who has sent
2999 comments on this specification over the years.</p>
3001 <p>The working group would like to extend special thanks to Donna
3002 McManus, Justin Baker, Joel Sklar, and Molly Ives Brower who perfermed
3003 the final editorial review.</p>
3005 <h2><a name=references>16. References</a></h2>
3009 <dt>[CSS1]
3010 <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
3013 <dt>[CSS21]
3014 <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
3017 <dt>[CWWW]
3018 <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
3021 <dt>[FLEX]
3022 <dd><a name="refsFLEX"></a> "<cite>Flex: The Lexical Scanner Generator</cite>", Version 2.3.7, ISBN 1882114213
3024 <dt>[HTML4]
3025 <dd><a name="refsHTML4"></a> Dave Ragget, Arnaud Le Hors, Ian Jacobs, editors; "<cite>HTML 4.01 Specification</cite>", W3C Recommendation, 24 December 1999
3028 <dt>[MATH]
3029 <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
3030 <dd>(<code><a href="http://www.w3.org/TR/REC-MathML/">http://www.w3.org/TR/REC-MathML/</a></code>)
3032 <dt>[RFC3066]
3033 <dd><a name="refsRFC3066"></a> H. Alvestrand; "<cite>Tags for the Identification of Languages</cite>", Request for Comments 3066, January 2001
3034 <dd>(<a href="http://www.ietf.org/rfc/rfc3066.txt"><code>http://www.ietf.org/rfc/rfc3066.txt</code></a>)
3036 <dt>[STTS]
3037 <dd><a name=refsSTTS></a> Daniel Glazman; "<cite>Simple Tree Transformation Sheets 3</cite>", Electricité de France, submission to the W3C, 11 November 1998
3038 <dd>(<code><a href="http://www.w3.org/TR/NOTE-STTS3">http://www.w3.org/TR/NOTE-STTS3</a></code>)
3040 <dt>[SVG]
3041 <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
3044 <dt>[UNICODE]</dt>
3046 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>.
3047 <dd>(<code><a href="http://www.unicode.org/versions/">http://www.unicode.org/versions/</a></code>)</dd>
3049 <dt>[XML10]
3050 <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
3053 <dt>[XMLNAMES]
3054 <dd><a name="refsXMLNAMES"></a> Tim Bray, Dave Hollander, Andrew Layman, editors; "<cite>Namespaces in XML</cite>", W3C Recommendation, 14 January 1999
3055 <dd>(<a href="http://www.w3.org/TR/REC-xml-names/"><code>http://www.w3.org/TR/REC-xml-names/</code></a>)
3057 <dt>[YACC]
3058 <dd><a name="refsYACC"></a> S. C. Johnson; "<cite>YACC — Yet another compiler compiler</cite>", Technical Report, Murray Hill, 1975
3060 </dl>
3061 </body>
3062 </html>