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An HTML element is a type of HTML (Hypertext Markup Language) document component, one of several types of HTML nodes (there are also text nodes, comment nodes and others).[vague] HTML document is composed of a tree of simple HTML nodes, such as text nodes, and HTML elements, which add semantics and formatting to parts of document (e.g., make text bold, organize it into paragraphs, lists and tables, or embed hyperlinks and images). Each element can have HTML attributes specified. Elements can also have content, including other elements and text.
HTML documents are delivered as "documents".[note 1] These are then parsed, which turns them into the Document Object Model (DOM) internal representation, within the web browser.[note 2][note 3] Presentation by the web browser (such as screen rendering or access by JavaScript) is then performed on this internal DOM, not the original document.
Early HTML documents (and to a lesser extent today's HTML documents) were largely invalid HTML and riddled with syntax errors. The parsing process was also required to "fix" these errors as best it could. The result was often not correct (i.e., it did not represent what a careless coder had originally intended) but was at least valid according to the HTML standard. Only in the rarest cases would the parser abandon parsing altogether.
As is generally understood, the position of an element is indicated as spanning from a start tag, possibly including some child content, and is terminated by an end tag.[3] This is the case for many, but not all, elements within an HTML document. The distinction is explicitly emphasised in HTML 4.01 Specification:
Elements are not tags. Some people refer to elements as tags (e.g., "the P tag"). Remember that the element is one thing, and the tag (be it start or end tag) is another. For instance, the HEAD element is always present, even though both start and end HEAD tags may be missing in the markup.[3]
Similarly the W3C Recommendadtion HTML 5.1 2nd Edition explicitly says:
Tags are used to delimit the start and end of elements in the markup. (...) The start and end tags of certain normal elements can be omitted, (...)
The contents of the element must be placed between just after the start tag (which might be implied, in certain cases) and just before the end tag (which again, might be implied, in certain cases).
and:
Certain tags can be omitted.
NOTE:
Omitting an element's start tag (...) does not mean the element is not present; it is implied, but it is still there. For example, an HTML document always has a root <html> element, even if the string <html> doesn't appear anywhere in the markup.
As HTML (before HTML5) is based on SGML,[4] its parsing also depends on the Document Type Definition (DTD), specifically an HTML DTD (e.g. HTML 4.01[5][note 4]). The DTD specifies which element types are possible (i.e. it defines the set of element types) and also the valid combinations in which they may appear in a document. It is part of general SGML behavior that, where only one valid structure is possible (per the DTD), its explicit statement in any given document is not generally required. As a simple example, the <p> tag indicating the start of a paragraph element should be complemented by a </p> tag indicating its end. But since the DTD states that paragraph elements cannot be nested, an HTML document fragment <p>Para 1 <p>Para 2 <p>Para 3is thus inferred to be equivalent to <p>Para 1 </p><p>Para 2 </p><p>Para 3. (If one paragraph element cannot contain another, any currently open paragraph must be closed before starting another.) Because this implication is based on the combination of the DTD and the individual document, it is not usually possible to infer elements from document tags alone but only by using an SGML—or HTML—aware parser with knowledge of the DTD. HTML5 creates a similar result by defining what tags can be omitted.[6]
SGML is complex, which has limited its widespread understanding and adoption. XML was developed as a simpler alternative. Although both can use the DTD to specify the supported elements and their permitted combinations as document structure, XML parsing is simpler. The relation from tags to elements is always that of parsing the actual tags included in the document, without the implied closures that are part of SGML.[note 5]
HTML as used on the current web is likely to be either treated as XML, by being XHTML, or as HTML5; in either case the parsing of document tags into DOM elements is simplified compared to legacy HTML systems. Once the DOM of elements is obtained, behavior at higher levels of interface (example: screen rendering) is identical or nearly so.[note 6]
%block; vs. boxPart of this CSS presentation behavior is the notion of the "box model". This is applied to those elements that CSS considers to be "block" elements, set through the CSS display: block; declaration.
HTML also has a similar concept, although different, and the two are very frequently confused. %block; and %inline; are groups within the HTML DTD that group elements as being either "block-level" or "inline".[8] This is used to define their nesting behavior: block-level elements cannot be placed into an inline context.[note 7] This behavior cannot be changed; it is fixed in the DTD. Block and inline elements have the appropriate and different CSS behaviors attached to them by default,[8] including the relevance of the box model for particular element types.
Note though that this CSS behavior can, and frequently is, changed from the default. Lists with <ul><li> ... are %block; elements and are presented as block elements by default. However, it is quite common to set these with CSS to display as an inline list.[9]
In the HTML syntax, most elements are written with a start tag and an end tag, with the content in between. An HTML tag is composed of the name of the element, surrounded by angle brackets. An end tag also has a slash after the opening angle bracket, to distinguish it from the start tag. For example, a paragraph, which is represented by the <p> element, would be written as:
<p>In the HTML syntax, most elements are written ...</p>
However, not all of these elements require the end tag, or even the start tag, to be present.[6] Some elements, the so-called void elements, do not have an end tag. A typical example is the <br> (hard line-break) element. A void element's behavior is predefined, and it cannot contain any content or other elements. For example, an address would be written as:
<p>P. Sherman<br>42 Wallaby Way<br>Sydney</p>
When using XHTML, it is required to open and close all elements, including void elements. This can be done by placing an end tag immediately after the start tag, but this is not legal in HTML 5 and will lead to two elements being created. An alternative way to specify that it is a void element, which is compatible with both XHTML and HTML 5, is to put a / at the end of the tag (not to be confused with the / at the beginning of a closing tag).
<p>P. Sherman<br />42 Wallaby Way<br />Sydney</p>
HTML attributes are specified inside the start tag. For example, the <abbr> element, which represents an abbreviation, expects a title attribute within its opening tag. This would be written as:
<abbr title="abbreviation">abbr.</abbr>
There are multiple kinds of HTML elements: normal elements, raw text elements, and void elements.
Normal elements usually have both a start tag and an end tag, although for some elements the end tag, or both tags, can be omitted. It is constructed in a similar way:
<tag>) marking the beginning of an element, which may incorporate any number of HTML attributes;</tag>.Raw text elements (also known as text or text-only elements) are constructed with:
<tag>) marking the beginning of an element, which may incorporate any number of HTML attributes;</tag>. In some versions of HTML, the end tag is optional for some elements. The end tag is required in XHTML.An example is the <title> element must not contain other elements (including markup of text), only plain text.
Void elements (also sometimes called empty elements, single elements or stand-alone elements) only have a start tag (in the form <tag>), which contains any HTML attributes. They may not contain any children, such as text or other elements. For compatibility with XHTML, the HTML specification allows an optional space and slash (<tag /> is permissible). The space and slash are required in XHTML and other XML applications. Two common void elements are <br /> (for a hard line-break, such as in a poem or an address) and <hr /> (for a thematic break). Other such elements are often place-holders which reference external files, such as the image (<img />) element. The attributes included in the element will then point to the external file in question. Another example of a void element is <link />, for which the syntax is:
<link rel="stylesheet" href="fancy.css" type="text/css">
This <link /> element points the browser at a style sheet to use when presenting the HTML document to the user. Note that in the HTML syntax attributes don't have to be quoted if they are composed only of certain characters: letters, digits, the hyphen-minus and the period. When using the XML syntax (XHTML), on the other hand, all attributes must be quoted, and a spaced trailing slash is required before the last angle bracket:
<link rel="stylesheet" href="fancy.css" type="text/css" />
HTML attributes define desired behavior or indicate additional element properties. Most attributes require a value. In HTML, the value can be left unquoted if it does not include spaces (attribute=value), or it can be quoted with single or double quotes (attribute='value' or attribute="value"). In XML, those quotes are required.
Boolean attributes, on the other hand, don't require a value to be specified. An example is the checked for checkboxes:
<input type=checkbox checked>
In the XML (and thus XHTML) syntax, though, the name should be repeated as the value:
<input type="checkbox" checked="checked" />
Informally, HTML elements are sometimes referred to as "tags" (an example of synecdoche), though many prefer the term tag strictly in reference to the markup delimiting the start and end of an element.
Element (and attribute) names may be written in any combination of upper or lower case in HTML, but must be in lower case in XHTML.[10] The canonical form was upper-case until HTML 4, and was used in HTML specifications, but in recent years, lower-case has become more common.
HTML elements are defined in a series of freely available open standards issued since 1995, initially by the IETF and subsequently by the W3C.
During the browser wars of the 1990s, developers of user agents (e.g. web browsers) often developed their own elements, some of which have been adopted in later standards. Other user agents may not recognize non-standard elements, and they will be ignored, possibly causing the page to be displayed improperly.
In 1998, XML (a simplified form of SGML) introduced mechanisms to allow anyone to develop their own elements and incorporate them in XHTML documents, for use with XML-aware user agents.[11]
Subsequently, HTML 4.01 was rewritten in an XML-compatible form, XHTML 1.0 (eXtensible HTML). The elements in each are identical, and in most cases valid XHTML 1.0 documents will be valid or nearly valid HTML 4.01 documents. This article mainly focuses on real HTML, unless noted otherwise; however, it remains applicable to XHTML. See HTML for a discussion of the minor differences between the two.
Since the first version of HTML, several elements have become outmoded, and are deprecated in later standards, or do not appear at all, in which case they are invalid (and will be found invalid, and perhaps not displayed, by validating user agents).[12]
In HTML 4.01 / XHTML 1.0, the status of elements is complicated by the existence of three types of DTD:
HTML5 instead provides a listing of obsolete features to go along with the standardized normative content. They are broken down into "obsolete but conforming" for which implementation instructions exist and "non-conforming" ones that should be replaced.[13]
The first Standard (HTML 2.0) contained four deprecated elements, one of which was invalid in HTML 3.2. All four are invalid in HTML 4.01 Transitional, which also deprecated a further ten elements. All of these, plus two others, are invalid in HTML 4.01 Strict. While the frame elements are still current in the sense of being present in the Transitional and Frameset DTDs, there are no plans to preserve them in future standards, as their function has been largely replaced, and they are highly problematic for user accessibility.
(Strictly speaking, the most recent XHTML standard, XHTML 1.1 (2001), does not include frames at all; it is approximately equivalent to XHTML 1.0 Strict, but also includes the Ruby markup module.)[14]
A common source of confusion is the loose use of deprecated to refer to both deprecated and invalid status, and to elements that are expected to be formally deprecated in the future.
Since HTML 4, HTML has increasingly focused on the separation of content (the visible text and images) from presentation (like color, font size, and layout).[15] This is often referred to as a separation of concerns. HTML is used to represent the structure or content of a document, its presentation remains the sole responsibility of CSS style sheets. A default style sheet is suggested as part of the CSS standard, giving a default rendering for HTML.[16]
Behavior (interactivity) is also kept separate from content, and is handled by scripts. Images are contained in separate graphics files, separate from text, though they can also be considered part of the content of a page.
Separation of concerns allows the document to be presented by different user agents according to their purposes and abilities. For example, a user agent can select an appropriate style sheet to present a document by displaying on a monitor, printing on paper, or to determine speech characteristics in an audio-only user agent. The structural and semantic functions of the markup remain identical in each case.
Historically, user agents did not always support these features. In the 1990s, as a stop-gap, presentational elements (like <b> and <i>) were added to HTML, at the cost of creating problems for interoperability and user accessibility. This is now regarded as outmoded and has been superseded by style sheet-based design; most presentational elements are now deprecated.[17]
External image files are incorporated with the <img /> or <object /> elements. (With XHTML, the SVG language can also be used to write graphics within the document, though linking to external SVG files is generally simpler.)[18] Where an image is not purely decorative, HTML allows replacement content with similar semantic value to be provided for non-visual user agents.
An HTML document can also be extended through the use of scripts to provide additional behaviors beyond the abilities of HTML hyperlinks and forms.
The elements <style> and <script>, with related HTML attributes, provide style sheets and scripts.
<style /> and <script /> may link to shared external documents, or <style>...</style> and <script>...</script> may contain embedded instructions. (The <link> element can also be used to link style sheets.)<script /> or <script>...</script> can occur at any point in the document (head or body).style attribute is valid in most document body elements (e.g. <div style="...">) for inclusion of inline style instructions.<noscript>...</noscript> element provides embedded alternative content where appropriate; however, it can only be used in the document head and in the body as a block-level element.<html>...</html>
<head>...</head>
<body>...</body>
<base />
href and other links in the document. Must appear before any element that refers to an external resource. HTML permits only one <base> element for each document. This element has HTML attributes, but no contents.BASE) is mentioned in HTML Tags; standardized in HTML 2.0; still current.<basefont /> (deprecated)
<font> elements. Deprecated in favor of style sheets.<isindex /> (deprecated)
<isindex> could either appear in the document head or in the body, but only once in a document. See Forms.<link />
<link rel="stylesheet" type="text/css" href="url" title="description_of_style">[20]<link rel="next" href="url"><head> element may contain any number of <link /> elements. This element has HTML attributes, but no contents.LINK existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current.<meta />
<meta /> elements specify associative key-value pairs. In general, a meta element conveys hidden information about the document. Several meta tags can be used, all of which should be nested in the head element. The specific purpose of each <meta /> element is defined by its attributes. Outside of XHTML, it is often given without the slash (<meta>), despite being a void element.<meta /> elements can specify HTTP headers which should be sent by a web server before the actual content. For example, <meta http-equiv="foo" content="bar" /> specifies that the page should be served with an HTTP header called foo that has a value bar.<meta /> element specifies name and associated content HTML attributes describing aspects of the HTML page. To prevent possible ambiguity, an optional third attribute, scheme, may be supplied to specify a semantic framework that defines the meaning of the key and its value. For example, in <meta name="foo" content="bar" scheme="DC" /> the <meta /> element identifies itself as containing the foo element, with a value of bar, from the DC or Dublin Core resource description framework.<object>...</object>
<head> element, it could potentially be used to extract foreign data and associate it with the current document.<script>...</script>
src attribute.[21] Also usable in the document body to dynamically generate either both block or inline content.<style>...</style>
<style type="text/css"> ... </style>@import directives of the form:
<style> @import url; </style>[22]<title>...</title>
<title> element must not contain other elements, only text. Only one <title> element is permitted in a document.In visual browsers, displayable elements can be rendered as either block or inline. While all elements are part of the document sequence, block elements appear within their parent elements:
Conversely, inline elements are treated as part of the flow of document text; they cannot have margins, width or height set, and do break across lines.
Block elements, or block-level elements, have a rectangular structure. By default, these elements will span the entire width of its parent element, and will thus not allow any other element to occupy the same horizontal space as it is placed on.
The rectangular structure of a block element is often referred to as the box model, and is made up of several parts. Each element contains the following:
The above section refers only to the detailed implementation of CSS rendering and has no relevance to HTML elements themselves.
<p>...</p>
P existed in HTML Tags, and was standardized in HTML 2.0; still current.<h1>...</h1>
<h2>...</h2>
<h3>...</h3>
<h4>...</h4>
<h5>...</h5>
<h6>...</h6>
h1 delimits the highest-level heading, h2 the next level down (sub-section), h3 for a level below that, and so on to h6. They are sometimes referred to collectively as hn tags, n meaning any of the available heading levels.<dl>...</dl>
DL existed in HTML Tags, and was standardized in HTML 2.0; still current.<dt>...</dt>
DT existed in HTML Tags, and was standardized in HTML 2.0; still current.<dd>...</dd>
DD existed in HTML Tags, and was standardized in HTML 2.0; still current.<ol>...</ol>
type attribute can be used to specify the kind of marker to use in the list, but style sheets give more control. The default is Arabic numbering. In an HTML attribute: <ol type="foo">; or in a CSS declaration: ol { list-style-type: foo; } – replacing foo with one of the following:
| Style | HTML value | CSS value |
|---|---|---|
| A, B, C ... | A |
upper-alpha
|
| a, b, c ... | a |
lower-alpha
|
| I, II, III ... | I |
upper-roman
|
| i, ii, iii ... | i |
lower-roman
|
| 1, 2, 3 ... | 1 |
decimal
|
CSS provides several other options not available as pure-HTML markup, including none, and options for CJK, Hebrew, Georgian, and Armenian script.
OL existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current.<ul>...</ul>
<ul type="foo">; or in a CSS declaration: ul { list-style-type: foo; } – replacing foo with one of the following (the same values are used in HTML and CSS): disc (the default), square, or circle. Only the CSS method is supported in HTML5. CSS also provides none, and the ability to replace these bullets with custom images.UL existed in HTML Tags, and was standardized in HTML 2.0; still current.<li>...</li>
ol) or unordered (ul) lists.LI existed in HTML Tags, and was standardized in HTML 2.0; still current.<dir>...</dir> (deprecated)
<ul>.DIR existed in HTML Tags, and was standardized in HTML 2.0; deprecated in HTML 4.0 Transitional; invalid in HTML 4.0 Strict.<address>...</address>
ADDRESS existed in HTML Tags, and was standardized in HTML 2.0; still current.<article>...</article>
<aside>...</aside>
<blockquote>...</blockquote>
cite attribute (not to be confused with the <cite> element) may give the source, and must be a fully qualified Uniform Resource Identifier.<q>) element.BLOCKQUOTE existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current. See blockquote element for more information.<center>...</center> (deprecated)
<div> or another element with centering defined using style sheets.<del>...</del>
<div>...</div>
<figure>...</figure>
<figcaption>.<figcaption>...</figcaption>
<figure> element.<footer>...</footer>
<header>...</header>
<hr />
<ins>...</ins>
<main>...</main>
<menu>...</menu> (deprecated)
<ul> list.MENU existed in HTML Tags, and was standardized in HTML 2.0; deprecated in HTML 4.0 Transitional; invalid in HTML 4.0 Strict; then redefined in HTML5, but removed in HTML 5.2.<nav>...</nav>
<noscript>...</noscript>
<pre>...</pre>
<pre>...</pre>, white-space should be rendered as authored. (With the CSS properties: { white-space: pre; font-family: monospace; }, other elements can be presented in the same way.) This element can contain any inline element except: <image>, <object>, <big>, <small>, <sup>, and <sub>...</sub>.PRE existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current.<section>...</section>
<div> in that it is only used to contain sections of a page, which the W3C defines as a group of content with a similar theme.<script>...</script>
<script /> with a src attribute to supply a URL from which to load the script, or used as <script>...</script> around embedded script content.
<script> is not itself either a block or inline element; by itself it should not display at all, but it can contain instructions to dynamically generate either both block or inline content.Inline elements cannot be placed directly inside the <body> element; they must be wholly nested within block-level elements.[26]
<a>...</a>
href,[28] the anchor becomes a hyperlink to either another part of the document or another resource (e.g. a webpage) using an external URL. Alternatively (and sometimes concurrently), with the name or id HTML attributes set, the element becomes a link target. A Uniform Resource Locator (URL) can link to this target via a fragment identifier. In HTML5, any element can now be made into a target by using the id attribute,[29] so using <a name="foo">...</a> is not necessary, although this way of adding anchors continues to work.<h2><a name="contents">Table of contents</a></h2><a href="http://example.com#contents">see contents</a><a href="#contents">contents, above</a>title may be set to give brief information about the link:
<a href="URL" title="additional information">link text</a>title value is displayed in a tooltip or in some other manner. Some browsers render alt text the same way, although this is not what the specification calls for.A existed in HTML Tags, and was standardized in HTML 2.0; still currentPhrase elements are used for marking up phrases and adding structure or semantic meaning to text fragments. For example, the <em> and <strong> tags can be used for adding emphasis to text.
<abbr>...</abbr>
<abbr title="abbreviation">abbr.</abbr><acronym>...</acronym> (deprecated)
<abbr> element, but marks an acronym:
<acronym title="Hyper-Text Mark-up Language">HTML</acronym>abbr tag.[30]<dfn>...</dfn>
DFN existed in HTML Internet Draft 1.2, and was fully standardized in HTML 3.2; still current.<em>...</em>
EM existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current.<strong>...</strong>
STRONG existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current, redefined in HTML5.These elements are useful primarily for documenting computer code development and user interaction through differentiation of source code (<code>), variables (<var>), user input (<kbd>), and terminal or other output (<samp>).
<code>...</code>
code example). Conventionally rendered in a mono-space font.CODE existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current.<kbd>...</kbd>
KBD existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current.<samp>...</samp>
SAMP existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current.<var>...</var>
VAR existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current.As visual presentational markup only applies directly to visual browsers, its use is discouraged. Style sheets should be used instead. Several of these elements are deprecated or invalid in HTML 4 / XHTML 1.0, and the remainder are invalid in the current draft of XHTML 2.0. The current draft of HTML5, however, re-includes <s>, <u>, and <small>, assigning new semantic meaning to each. In an HTML5 document, the use of these elements is no longer discouraged, provided that it is semantically correct.
<b>...</b>
{ font-weight: bold; }. The <strong> element usually has the same effect in visual browsers, as well as having more semantic meaning, under HTML 4.01.<b> has its own meaning, distinct from that of <strong>. It denotes "text to which attention is being drawn for utilitarian purposes without conveying any extra importance and with no implication of an alternate voice or mood."[31]B existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current, redefined in HTML5.<i>...</i>
{ font-style: italic; }. Using <em>...</em> has the same visual effect in most browsers, as well as having a semantic meaning as emphasis, under HTML 4.01. (Purely typographic italics have many non-emphasis purposes, as HTML 5 more explicitly recognized.)<i> has its own semantic meaning, distinct from that of <em>. It denotes "a different quality of text" or "an alternative voice or mood "e.g., a thought, a ship name, a binary species name, a foreign-language phrase, etc."[32]I existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current, redefined in HTML5.<u>...</u>
{ text-decoration: underline; }. Deprecated in HTML 4.01. Restored in HTML5.<u> element denotes "a span of text with an unarticulated, though explicitly rendered, non-textual annotation, such as labelling the text as being a proper name in Chinese text (a Chinese proper name mark), or labelling the text as being misspelt." The HTML5 specification reminds developers that other elements are almost always more appropriate than <u> and admonishes designers not to use underlined text where it could be confused for a hyper-link.[33]U existed in HTML Internet Draft 1.2, was standardized in HTML 3.2 but was deprecated in HTML 4.0 Transitional and was invalid in HTML 4.0 Strict. Reintroduced in HTML5.<small>...</small>
{ font-size: smaller; }<small> element denotes "side comments such as small print."[34] This has caused some confusion with the <aside>...</aside> element.<s>...</s>
<strike>.<s> element denotes information that is "no longer accurate or no longer relevant", and is not to be confused with <del>, which indicates removal/deletion.[35]S was deprecated in HTML 4.0 Transitional (having not appeared in any previous standard), and was invalid in HTML 4.0 Strict. Reintroduced in HTML5, which instead deprecated <strike>.<big>...</big> (deprecated)
{ font-size: larger; }<strike>...</strike> (deprecated)
{ text-decoration: line-through; })STRIKE was standardized in HTML 3.2; deprecated in HTML 4.0 Transitional; invalid in HTML 4.0 Strict.<tt>...</tt> (deprecated)
{ font-family: monospace; })TT existed in HTML Internet Draft 1.2, and was Standardized in HTML 2.0; not supported[36] in HTML5. Possible replacements: <kbd> for marking user input, <var> for variables (usually rendered italic, and not with a change to monospace), <code> for source code, <samp> for output.[36]<font>...</font> (deprecated)
<font [color=<var>color</var>] [size=<var>size</var>] [face=<var>face</var>]>...</font>color attribute (note the American spelling), typeface with the face attribute, and absolute or relative size with the size attribute.<font color="green">text</font> creates green text.<font color="#114499">text</font> creates text with hexadecimal color #114499.<font size="4">text</font> creates text with size 4. Sizes are from 1 to 7. The standard size is 3, unless otherwise specified in the <body> or other tags.<font size="+1">text</font> creates text with size 1 bigger than the standard. <font size="-1">text</font> is opposite.<font face="Courier">text</font> makes text with Courier font.<font size="N"> corresponds to {font-size: Yunits} (the HTML specification does not define the relationship between size N and unit-size Y, nor does it define a unit).<font color="red"> corresponds to { color: red; }<font face="Times New Roman"> corresponds to { font-family: 'Times New Roman', Times, serif; } – CSS supports a font stack, of two or more alternative fonts.<span>...</span>
<br />
<bdi>...</bdi>
<bdo>...</bdo>
<cite>...</cite>
<cite> was for "a citation or a reference to other sources" without any particular limitations or requirements.[38] The W3C HTML 5 spec uses a refinement of this idea, reflecting how the element has historically been used, but now requiring that it contain (but not be limited to) at least one of "the title of the work or the name of the author (person, people or organization) or an URL reference, or a reference in abbreviated form as per the conventions used for the addition of citation metadata."[39] But the WHATWG spec only permits the element to be used around the title of a work.[40] The W3C specs began with the broader definition, then switched to the very narrow one after WHATWG made this change. However, W3C reverted their own change in 2012, in response to negative developer-community feedback; the element was in broadly-deployed use with the broader scope, e.g., various blog and forum platforms wrap commenters' IDs and e-mail addresses in <cite>...</cite>, and people using the element for bibliographic citations were (and still are) routinely wrapping each entire citation in this element.<data>...</data>
<del>...</del>
<ins>...</ins>
<del> or <s>. Typically rendered underlined: Inserted text.<ins> and <del> elements may also be used as block elements: containing other block and inline elements. However, these elements must still remain wholly within their parent element to maintain a well-formed HTML document. For example, deleting text from the middle of one paragraph across several other paragraphs and ending in a final paragraph would need to use three separate <del> elements. Two <del> elements would be required as inline elements to indicate the deletion of text in the first and last paragraphs, and a third, used as a block element, to indicate the deletion in the intervening paragraphs.<mark>...</mark>
<q>...</q>
<blockquote>). Quote elements may be nested.<q> should automatically generate quotation marks in conjunction with style sheets. Practical concerns due to browser non-compliance may force authors to find workarounds.cite attribute gives the source, and must be a fully qualified URI.block-quote) using style sheets. For example, with a suitable CSS rule associated with q.lengthy: <q>Lengthy quote here.</q ><rb>...</rb>
<rp>...</rp>
<rt>...</rt>
<rtc>...</rtc>
<ruby>...</ruby>
<script>...</script>
<script> is not itself either a block or inline element; by itself it should not display at all, but it can contain instructions to dynamically generate either both block or inline content.<sub>...</sub>
and <sup>...</sup>
{ vertical-align: sub; } and { vertical-align: super; }, respectively.)<template>...</template>
<time>...</time>
<wbr />
<applet>...</applet> (deprecated)
<object>, as it could only be used with Java applets, and had accessibility limitations.<object> are not consistent between different browsers.<area />
<map>.<audio>...</audio>
src attribute. Supported audio formats vary from browser to browser.<canvas>...</canvas>
<embed>...</embed>
<object>, but then was added back into the HTML5 specification[48][49]<img />
src attribute specifies the image URL. The required alt attribute provides alternative text in case the image cannot be displayed.[50] (Though alt is intended as alternative text, Microsoft Internet Explorer 7 and below render it as a tooltip if no title attribute is given.[51]Safari and Google Chrome, on the other hand, do not display the alt attribute at all.)[52] The <img /> element was first proposed by Marc Andreessen and implemented in the NSCA Mosaic web browser.[53]IMG existed in HTML Internet Draft 1.2, and was standardized in HTML 2.0; still current.<map>...</map>
<object>...</object>
type attribute. This may be in any MIME-type the user agent understands, such as an embedded HTML page, a file to be handled by a plug-in such as Flash, a Java applet, a sound file, etc.<param />
<applet>, this element is now used with <object>, and should only occur as a child of <object>. It uses HTML attributes to set a parameter for the object, e.g. width, height, font, background color, etc., depending on the type of object. An object can have multiple <param /> elements.<source>...</source>
src attribute in a way similar to the <video> and <audio> elements.<track>...</track>
<video>...</video>
src attribute. Supported video formats vary from browser to browser.These elements can be combined into a form or in some instances used separately as user-interface controls; in the document, they can be simple HTML or used in conjunction with Scripts. HTML markup specifies the elements that make up a form, and the method by which it will be submitted. However, some form of scripts (server-side, client-side, or both) must be used to process the user's input once it is submitted.
(These elements are either block or inline elements, but are collected here as their use is more restricted than other inline or block elements.)
<form action="url">...</form>
<form> element specifies and operates the overall action of a form area, using the required action attribute.<button>...</button>
<datalist>...</datalist>
options for use in form elements.<fieldset>...</fieldset>
<fieldset>, which can then have a <legend> added in order to identify their function.<input />
<input> elements allow a variety of standard form controls to be implemented.<button> is preferred if possible (i.e., if the client supports it) as it provides richer possibilities.src attribute.size attribute specifies the default width of the input in character-widths. max-length sets the maximum number of characters the user can enter (which may be greater than size).text which produces a search bar.text. The difference is that text typed in this field is masked – characters are displayed as an asterisk, a dot, or another replacement. The password is still submitted to the server as plaintext, so an underlying secure communication protocol like HTTPS is needed if confidentiality is a concern.text for telephone numbers.text for email addresses.text for URLs.text for numbers.hidden inputs are not visible in the rendered page, but allow a designer to maintain a copy of data that needs to be submitted to the server as part of the form. This may, for example, be data that this web user entered or selected on a previous form that needs to be processed in conjunction with the current form. Not displayed to the user but data can still be altered client-side by editing the HTML source.<isindex /> (deprecated)
<isindex /> could either appear in the document head or in the body, but only once in a document.<isindex /> operated as a primitive HTML search form; but was de facto obsoleted by more advanced HTML forms introduced in the early to mid-1990s. Represents a set of hyperlinks composed of a base URI, an ampersand and percent-encoded keywords separated by plus signs.ISINDEX existed in HTML Tags; standardized in HTML 2.0; deprecated in HTML 4.0 Transitional; invalid in HTML 4.0 Strict.<keygen>...</keygen> (deprecated)
<label for="id">...</label>
radio. Clicking on the label fires a click on the matching input.<legend>...</legend>
<fieldset>.<meter>...</meter>
value attribute. Can also have: min, low, high, and max.<option value="x">...</option>
<select> list.<optgroup>...</optgroup>
<option> elements in a <select> list.<output>...</output>
<progress>...</progress>
<select name="xyz">...</select>
<textarea rows="8">...</textarea>
cols (where a column is a one-character width of text) and rows HTML attributes. The content of this element is restricted to plain text, which appears in the text area as default text when the page is loaded.The format of HTML Tables was proposed in the HTML 3.0 Drafts and the later RFC 1942 HTML Tables. They were inspired by the CALS Table Model. Some elements in these proposals were included in HTML 3.2; the present form of HTML Tables was standardized in HTML 4. (Many of the elements used within tables are neither block nor inline elements.)
<table>...</table>
summary attribute is informally required for accessibility purposes, though its usage is not simple.<tr>...</tr>
<table>.<th>...</th>
<table> header cell; contents are conventionally displayed bold and centered. An aural user agent may use a louder voice for these items.<td>...</td>
<table> data cell.<colgroup>...</colgroup>
<table>.<col>...</col>
<table>.<caption>...</caption>
<table>.<thead>...</thead>
<table>. This section may be repeated by the user agent if the table is split across pages (in printing or other paged media).<tbody>...</tbody>
<table>.<tfoot>...</tfoot>
<table>. Like <thead>, this section may be repeated by the user agent if the table is split across pages (in printing or other paged media).Frames allow a visual HTML browser window to be split into segments, each of which can show a different document. This can lower bandwidth use, as repeating parts of a layout can be used in one frame, while variable content is displayed in another. This may come at a certain usability cost, especially in non-visual user agents,[54] due to separate and independent documents (or websites) being displayed adjacent to each other and being allowed to interact with the same parent window. Because of this cost, frames (excluding the <iframe> element) are only allowed in HTML 4.01 Frame-set. Iframes can also hold documents on different servers. In this case the interaction between windows is blocked by the browser. Sites like Facebook and Twitter use iframes to display content (plugins) on third party websites. Google AdSense uses iframes to display banners on third party websites.
In HTML 4.01, a document may contain a <head> and a <body> or a <head> and a <frameset>, but not both a <body> and a <frameset>. However, <iframe> can be used in a normal document body.
<frameset>...</frameset> (deprecated)
<frame /> elements for a document. The layout of frames is given by comma separated lists in the rows and cols HTML attributes.<frame /> (deprecated)
<frameset>. A separate document is linked to a frame using the src attribute inside the <frame /> element.<noframes>...</noframes> (deprecated)
<frame /> elements.<iframe>...</iframe>
<object /> element, an <iframe> can be the "target" frame for links defined by other elements, and it can be selected by the user agent as the focus for printing, viewing its source, and so on.longdesc attributeIn HTML, longdesc is an attribute used within the <img />, <frame />, or <iframe> elements. It is supposed to be a URL[note 8] to a document that provides a long description for the image, frame, or iframe in question.[55] Note that this attribute should contain a URL, not – as is commonly mistaken – the text of the description itself.
longdesc was designed to be used by screen readers to display image information for computer users with accessibility issues, such as the blind or visually impaired, and is widely implemented by both web browsers and screen readers.[56] Some developers object that[57] it is actually seldom used for this purpose because there are relatively few authors who use the attribute and most of those authors use it incorrectly; thus, they recommend deprecating longdesc.[58] The publishing industry has responded, advocating the retention of longdesc.[59]
<img src="Hello.jpg" longdesc="description.html">
Content of description.html:
<br />
<p>This is an image of a two-layered birthday cake.</p>
...
Since very few graphical browsers support making the link available natively (Opera and iCab being the exceptions), it is useful to include a link to the description page near the <img /> element whenever possible, as this can also aid sighted users.
<img src="Hello.jpg" longdesc="description.html" /> [<a href=
"description.html" title="long description of the image">D</a>]
The following elements were part of the early HTML developed by Tim Berners-Lee from 1989 to 1991; they are mentioned in HTML Tags, but deprecated in HTML 2.0 and were never part of HTML standards.
<listing>...</listing> (deprecated)
<plaintext /> (deprecated)
<plaintext /> does not have an end tag as it terminates the markup and causes the rest of the document to be parsed as if it were plaintext.<plaintext /> existed in HTML Tags; deprecated in HTML 2.0; invalid in HTML 4.0.<xmp>...</xmp> (deprecated)
<nextid /> (deprecated)
This section lists some widely used obsolete elements, which means they are not used in valid code. They may not be supported in all user agents.
<blink>...</blink> (deprecated)
{text-decoration: blink} (This effect may have negative consequences for people with photosensitive epilepsy;[63] its use on the public Internet should follow the appropriate guidelines.)<blink> originated in Netscape Navigator and is mostly recognized by its descendants, including Firefox; deprecated or invalid in HTML 2.0 and later. Note that the replacement CSS tag, while standard, is not required to be supported.<layer>...</layer> (deprecated)
<layer> originated in Netscape 4; deprecated or invalid in HTML 4.01 and later.<marquee>...</marquee> (deprecated)
<marquee> originated in Microsoft Internet Explorer; deprecated or invalid in HTML 4.01 and later.<nobr>...</nobr> (deprecated)
{white-space: nowrap;}<nobr> is a proprietary element which is recognized by most browsers for compatibility reasons; deprecated or invalid in HTML 2.0 and later.<noembed>...</noembed> (deprecated)
<embed> or <object> element.<!-- A Comment -->A comment in HTML (and related XML, SGML and SHTML) uses the same syntax as the SGML comment or XML comment, depending on the doctype.
Unlike most HTML tags, comments do not nest.
The markup <!--Xbegin<!--Y-->Xend--> will yield the comment Xbegin<!--Y and the text Xend--> after it, or sometimes just Xend-->, depending on browser.
Comments can appear anywhere in a document, as the HTML parser is supposed to ignore them no matter where they appear so long as they are not inside other HTML tag structures (i.e., they cannot be used next to attributes and values; this is invalid markup: <span id="x1"<--for "extension one"--> style="..."<).
Comments can even appear before the doctype declaration; no other tags are permitted to do this.
However, not all browsers and HTML editors are fully compliant with the HTML syntax framework and may do unpredictable things under some syntax conditions. Defective handling of comments only affects about 5% of all browsers and HTML editors in use, and even then only certain versions are affected by comment mishandling issues (Internet Explorer 6 accounts for most of this high percentage).
There are a few compatibility quirks involving comments:
doctype will cause Internet Explorer 6 to use quirks mode for the HTML page. None of the doctype information will be processed.<style> and <script> elements are still sometimes surrounded by comment delimiters, and CSS- and script-capable browsers are written to specifically ignore that comment markup as not actually a comment. This means that attempts to actually comment out CSS and script markup by change the elements inside the comment to not be recognized, e.g. <-- [script]...[/script] -->.<style> ... {comment tags} ...</style> will show up on-screen. Other HTML editors may have this same defect.<object> for the inevitable exception.
<embed>
<embed>
...frames do present additional usability challenges that are unique to users with disabilities, particularly those who use screen readers.
By: Wikipedia.org
Edited: 2021-06-18 19:10:24
Source: Wikipedia.org