HTML attribute: Difference between revisions

Revision as of 19:00, 23 July 2022

Revision as of 17:51, 22 August 2022

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Usually, [[HTML element]]s can take any of several most common standard attributes ([[#Standard_attributes|See the complete list]]):

* The '''<code>id</code>''' can take attribute provides a document-wide unique identifier for an element.<ref>However, multiple identifiers may apply to the same element; in particular an element may be inside another element, each having an identifier.</ref><ref>{{Cite web|url=https://www.w3schools.com/html/html_id.asp|title=HTML id|website=www.w3schools.com|access-date=2020-04-27}}</ref><ref>{{Cite web|url=https://www.w3schools.com/tags/att_global_id.asp|title=HTML Global id Attribute|website=www.w3schools.com|access-date=2020-04-27}}</ref> This can be used as [[CSS selector]] to provide presentational properties, by browsers to focus attention on the specific element, or by scripts to alter the contents or presentation of an element. Appended to the URL of the page, the URL directly targets the specific element within the document, typically a sub-section of the page. For example, the ID "Attributes" in <code><nowiki>http://en.wikipedia.org/wiki/HTML#Attributes</nowiki></code> (to refer to the section "Attributes" in the "HTML" page).

* The '''<code>class</code>''' attribute provides a way of classifying similar elements.<ref>{{Cite web|url=https://www.w3schools.com/html/html_classes.asp|title=HTML Classes|website=www.w3schools.com|access-date=2020-04-27}}</ref><ref>{{Cite web|url=https://www.w3schools.com/tags/att_global_class.asp|title=HTML Global class Attribute|website=www.w3schools.com|access-date=2020-04-27}}</ref> This can be used for [[semantics|semantic]] purposes, or for presentation purposes. Semantically, for example, classes are used in [[microformat]]s. Presentationally, for example, an HTML document might use the designation <code>class="notation"</code> to indicate that all elements with this class value are subordinate to the main text of the document. Such elements might be gathered together and presented as footnotes on a page instead of appearing in the place where they occur in the HTML source. Another presentation use would be as a [[CSS selector]]. Multiple classes [[Variable_(computer_science)#Naming_conventions|can be added by having spaces between each Identifier]].

* An author may use the '''<code>style</code>''' non-attributal codes presentational properties to a particular element. The '''<code>style</code>''' attribute can be used on any HTML element (it will validate on any HTML element; however, it is not necessarily useful). It is considered better practice to use an element's <code>id</code> or <code>class</code> attributes to select the element with a [[Style sheet (web development)|stylesheet]], though sometimes this can be too cumbersome for a simple and specific or ad hoc application of styled properties.