Hypertext markup language attributes are special words used to adjust the behavior or display of anHTML element. An attribute either modifies the default functionality of an element type or provides functionality to certain element types unable to function correctly without them. InHTML syntax, an attribute is added to anHTML start tag.

Several basic attributes types have been recognized, including: (1)required attributes needed by a particular element type for that element type to function correctly; (2)optional attributes used to modify the default functionality of an element type; (3)standard attributes supported by many element types; and (4)event attributes used to cause element types to specify scripts to be run under specific circumstances.

Doctype HTML is a declaration that tells the browser what version of HTML the document is written in.

Some attribute types function differently when used to modify different element types. For example, the attributename is used by several element types, but has slightly different functions in each.^[1]

HTML attributes generally appear asname–value pairs, separated by=, and are written within the start tag of an element, after the element's name:

<elementattribute="value">elementcontent</element>

Whereelement names the HTML element type, andattribute is the name of the attribute, set to the providedvalue. The value may be enclosed in single or double quotes, although values consisting of certain characters can be left unquoted in HTML (but notXHTML).^[2][3] Leaving attribute values unquoted is considered unsafe.^[4]

Although most attributes are provided as paired names and values, some affect the element simply by their presence in the start tag of the element^[5] (like theismap attribute for theimg element^[6]).

The abbreviation element,abbr, can be used to demonstrate these various attributes:

<abbrid="anId"class="aClass"style="color:blue;"title="Hypertext Markup Language">HTML</abbr>

This example displays asHTML in blue without being a link, and in most browsers, pointing the cursor at the abbreviation should display the title text "HypertextMarkup Language" within a floating yellow background (tooltip).

<divstyle="text-align: center;">Centered text</div>

In this other example, your text will look like this:

Most elements also take the language-related attributeslang anddir.

Usually,HTML elements can take any of several most common standard attributes (See the complete list):

• Theid attribute provides a document-wide unique identifier for an element.^[7][8][9] This can be used asCSS 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" inhttp://en.wikipedia.org/wiki/HTML#Attributes (to refer to the section "Attributes" in the "HTML" page).
• Theclass attribute provides a way of classifying similar elements. Multiple class names can be added by separating them with spaces.^[10][11] Semantically, for example, classes are used inmicroformats. Additionally authors of style sheets can constructselectors that match elements by class for styling purposes. For example, a HTML document might use the designationclass="notation" to indicate that all elements with this class value are subordinate to the main text of the document. Such elements might be gathered together as footnotes on a page—instead of appearing in the place suggested by their position within the HTML source. The style sheet author might also define a rule with the.notation selector and define the propertyfont-size: small;.
• Thestyle attribute provides a way of applying element-specific style rules. Multiplestyle declarations can be added by separating them with semicolons and an optional space, where each declaration includes a CSS property name and a value separated by a colon and an optional space (Example:style="color: red; text-align: center;").^[12][13][14] Thestyle 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 add the style information to astyle sheet, often accomplished with selectors that match the element class or ID. Sometimes, however, inline styles are favored where style sheets are considered too cumbersome for a simple and specific or ad hoc style specification.
• Thetitle attribute is used to attach subtextual explanation to an element. In most browsers this attribute is displayed as what is often referred to as atooltip.

HTML attributes are generally classified asrequired attributes,optional attributes,standard attributes, andevent attributes:

• Usually the required and optional attributes modify specific HTML elements
• While the standard attributes can be applied to most HTML elements.^[15]
• Event attributes, added in HTML version 4, allow an element to specifyscripts to be run under specific circumstances.^[16]Scripts are what you can type in html solutions.Html Scripts are for what inmates know for.
• Html Scripts are what you can remember
• Sometimes html is understandable for sources

• <a> and<area>:
  • coords — coordinates of an<area> or a<link> within it.
  • shape — shape of an<area> or a<link> within it. Values: default, rect, circle, poly.
• <a> and<link>:
  • hreflang — Language code of the linked document. (<a>,<link>)
  • rel — Nature of the linked document (relative to the page currently displayed). Free text for<a>, but<link> uses a set of terms (alternate, appendix, bookmark, chapter, contents, copyright, glossary, help, home, index, next, prev, section, start, stylesheet, subsection).
  • rev — Nature of the currently displayed page (relative to the linked document). Varies for<a> and<link> as for rel.
• <applet> and<object>:
  • archive — archive URL(s) (<applet>,<object>)
  • codebase — base URL (<applet>,<object>)
• <basefont> and<font>:
  • color — text color(deprecated) (<basefont>,<font>)
  • face — font family(deprecated) (<basefont>,<font>)
• <col> and<colgroup>:
  • span — number of columns spanned (<col>,<colgroup>)
• <del> and<ins>:
  • datetime — date and time of textdeletion orinsertion.
• <form> and<input>:
  • accept — types of files accepted when uploading<form> or<input>
• <frame> and<iframe>:
  • frameborder — value (0 or 1) specifies whether to display a border around the<frame> or<iframe>.
  • marginheight — top and bottom margins in pixels around the<frame> or<iframe>.
  • scrolling — value (yes, no, auto) specifies whether to display scroll bars around the<frame> or<iframe>.
  • marginwidth — left and right margins in pixels around the<frame> or<iframe>.
• <frameset> and<textarea>:
  • cols — number of visible columns in<frameset> or<textarea>(some variation)
  • rows — number of visible rows in<frameset> or<textarea>(some variation)
• <img> and<object>:
  • usemap — specifies name of a map element to use with<img> -or- URL of an image-map to use with<object>.
• <input> and<textarea>:
  • readonly — specifies read-only text for<input> and<textarea>.
• <link> and<style>:
  • media — specifies display device for<link> and<style>. Values: all, aural, braille, handheld, print, projection, screen, tty, TV.
• <optgroup> and<option>:
  • label — description text for an<optgroup> or<option>.
• <td> and<th>:
  • abbr — abbreviated version of a tablecell orheader.
  • axis — category name for a tablecell orheader.
  • colspan — number of columns spanned by a tablecell orheader.
  • nowrap —(deprecated) prevents wrapping of a tablecell orheader.
  • rowspan — number of rows spanned by a tablecell orheader.
  • scope — no effect on normal browser display, but marks a tablecell orheader as a logical header for other cells. Values: col, colgroup, row, rowgroup.

• align —<applet>,<col>,<colgroup>,<object>,<tbody>,<td>,<tfoot>,<th>,<thead>

• align also deprecated in<caption>,<div>,<h1> to<h6>,<hr>,<iframe>,<img>,<input>,<legend>,<p>,<table>

• alt —<applet>,<area>,<img>,<input>
• bgcolor —<body>,<table>,<td>,<th>,<bgcolor>
• border —<img>,<object>,<table>
• char —<char>,<colgroup>,<tbody>,<td>,<tfoot>,<th>,<thead>,<tr>
• charoff —<col>,<colgroup>,<tbody>,<td>,<tfoot>,<th>,<thead>,<tr>
• charset —<a>,<link>,<script>
• cite —<blockquote>,<del>,<ins>,<q>
• compact —<dir>,<menu>,<ol>,<ul>
• disabled —<button>,<input>,<optgroup>,<option>,<select>,<textarea>
• height —<applet>,<iframe>,<img>,<object> . Also deprecated in<td>,<th>
• href —<a>,<area>,<base>,<link>
• hspace —<applet>,<object>. Also deprecated in<img>
• longdesc —<frame>,<iframe>,<img>
• name —<a>,<applet>,<button>,<form>,<frame>,<iframe>,<input>,<map>,<meta>,<object>,<param>,<select>,<textarea>
• size —<basefont>,<font>,<hr>,<input>,<select>
• src —<frame>,<iframe>,<img>,<input>,<script>
• target —<a>,<area>,<base>,<form>,<link>
• type —<button>,<input>,<li>,<link>,<object>,<ol>,<param>,<script>,<style>,<ul>
• valign —<col>,<colgroup>,<tbody>,<td>,<tfoot>,<th>,<thead>,<tr>
• value —<button>,<input>,<li>,<option>,<param>
• vspace —<applet>,<img>,<object>
• width —<applet>,<col>,<colgroup>,<hr>,<iframe>,<img>,<object>,<pre>,<table>,<td>,<th>

Standard attributes are also known asglobal attributes, and function with a large number of elements.^[17] They include the basic standard attributes: these includeaccesskey, class, contenteditable, contextmenu, data, dir, hidden, id, lang, style, tabindex, title. There are also some experimental ones. Bothxml:lang andxml:base have been deprecated. The multiplearia-* attributes improve accessibility.^[17] Theevent handler attributes are listed later on.

Technically all standard attributes must be accepted by all elements, though they will not function with some elements.^[18] The table below lists some common standard attributes, and some elements they can function with.

Element	id	class	style	title	dir	lang	xml:lang	accesskey	tabindex
<param>
<head>
<html>
<meta>
<title>
<style>
<applet>
<br>
<frame>
<frameset>
<iframe>
<basefont>
<center>
<dir>
<font>
<menu>
<s>
<strike>
<u>
<abbr>
<acronym>
<address>
<b>
<big>
<blockquote>
<body>
<caption>
<cite>
<code>
<col>
<colgroup>
<dd>
<del>
<dfn>
<div>
<dl>
<dt>
<em>
<fieldset>
<form>
<hr>
<h1>,<h2>,<h3>,<h4>,<h5>,<h6>
<i>
<img>
<ins>
<kbd>
<li>
<link>
<map>
<noframes>
<noscript>
<ol>
<optgroup>
<option>
<p>
<pre>
<q>
<samp>
<small>
<span>
<strong>
<sub>
<sup>
<table>
<tbody>
<td>
<tfoot>
<th>
<thead>
<tr>
<tt>
<ul>
<var>
<label>
<legend>
<object>
<select>
<a>
<area>
<button>
<input>
<textarea>

The standard attributes include theevent handler attributes. They are all prefixed on-:^[17]

Event attributes, added in HTML version 4, allow an element to specify scripts to be run under specific circumstances. The table below lists some common event handler attributes, and some elements they can function with.

Element	onload	onunload	onabort	onclick	ondblclick	onmousedown	onmousemove	onmouseout	onmouseover	onmouseup	onkeydown	onkeypress	onkeyup	onblur	onfocus	onchange	onselect
<frameset>
<body>
<abbr>
<acronym>
<address>
<b>
<big>
<blockquote>
<caption>
<center>
<cite>
<code>
<col>
<colgroup>
<dd>
<del>
<dfn>
<dir>
<div>
<dl>
<dt>
<em>
<fieldset>
<h1>,<h2>,<h3>,<h4>,<h5>,<h6>
<hr>
<i>
<ins>
<kbd>
<legend>
<li>
<link>
<map>
<menu>
<noframes>
<noscript>
<object>
<ol>
<optgroup>
<option>
<p>
<pre>
<q>
<s>
<samp>
<small>
<span>
<strike>
<strong>
<sub>
<sup>
<table>
<tbody>
<td>
<tfoot>
<th>
<thead>
<tr>
<tt>
<u>
<ul>
<var>
<img>
<a>
<area>
<button>
<form>
<label>
<select>
<input>
<textarea>

• HTML element