HOME

TheInfoList




The HyperText Markup Language, or HTML is the standard
markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable from the text, meaning when the document is processed for di ...
for documents designed to be displayed in a
web browser A web browser (commonly referred to as a browser) is application software Application software (app for short) is computing software designed to carry out a specific task other than one relating to the operation of the computer itself, typical ...

web browser
. It can be assisted by technologies such as
Cascading Style Sheets #REDIRECT CSS #REDIRECT CSS Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation Introduction A presentation conveys information from a speaker to an audience. Presentations are typically demonst ...

Cascading Style Sheets
(CSS) and
scripting language A scripting language or script language is a programming language A programming language is a formal language comprising a Instruction set architecture, set of instructions that produce various kinds of Input/output, output. Programming language ...
s such as
JavaScript JavaScript (), often abbreviated JS, is a programming language A programming language is a formal language comprising a Instruction set architecture, set of instructions that produce various kinds of Input/output, output. Programming lang ...

JavaScript
.
Web browser A web browser (commonly referred to as a browser) is application software Application software (app for short) is computing software designed to carry out a specific task other than one relating to the operation of the computer itself, typical ...

Web browser
s receive HTML documents from a
web server A web server is computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets of operations known as Computer program, pr ...
or from local storage and render the documents into multimedia web pages. HTML describes the structure of a
web page A web page (or webpage) is a hypertext File:Douglas Engelbart in 2008.jpg, Douglas Engelbart in 2009, at the 40th anniversary celebrations of "The Mother of All Demos" in San Francisco, a 90-minute 1968 presentation of the NLS (computer sy ...

web page
semantically Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of meaning, reference, or truth. The term can be used to refer to subfields of several distinct disciplines, including linguistics Linguistics is th ...

semantically
and originally included cues for the appearance of the document.
HTML element An HTML element is a type of (Hypertext Markup Language) document component, one of several types of HTML nodes (there are also text nodes, comment nodes and others). HTML document is composed of a of simple HTML , such as text nodes, and H ...
s are the building blocks of HTML pages. With HTML constructs,
images An image (from la, imago) is an artifact that depicts visual perception, such as a photograph or other Two-dimensional space, two-dimensional picture, that resembles a subject—usually a physical physical body, object—and thus provides ...
and other objects such as interactive forms may be embedded into the rendered page. HTML provides a means to create
structured document A structured document is an electronic document An electronic document is any electronic media content (other than computer program A computer program is a collection of instructions that can be executed by a computer to perform a specific tas ...
s by denoting structural
semantics Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another o ...
for text such as headings, paragraphs, lists,
links Link or Links may refer to: Places * Link, West Virginia, an unincorporated community in the US * Link River, Klamath Falls, Oregon, US People with the name * Link (singer) (Lincoln Browder, born 1964), American R&B singer * Link (surname) * ...

links
, quotes and other items. HTML elements are delineated by ''tags'', written using
angle brackets A bracket is either of two tall fore- or back-facing punctuation marks commonly used to isolate a segment of text or data from its surroundings. Typically deployed in symmetric pairs, an individual bracket may be identified as a ''left'' or ...
. Tags such as and directly introduce content into the page. Other tags such as surround and provide information about document text and may include other tags as sub-elements. Browsers do not display the HTML tags, but use them to interpret the content of the page. HTML can embed programs written in a
scripting language A scripting language or script language is a programming language A programming language is a formal language comprising a Instruction set architecture, set of instructions that produce various kinds of Input/output, output. Programming language ...
such as
JavaScript JavaScript (), often abbreviated JS, is a programming language A programming language is a formal language comprising a Instruction set architecture, set of instructions that produce various kinds of Input/output, output. Programming lang ...

JavaScript
, which affects the behavior and content of web pages. Inclusion of CSS defines the look and layout of content. The
World Wide Web Consortium The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary ...
(W3C), former maintainer of the HTML and current maintainer of the CSS standards, has encouraged the use of CSS over explicit presentational HTML A form of HTML, known as
HTML5 HTML5 is a used for structuring and presenting content on the . It is the fifth and last major version that is a (W3C) recommendation. The current specification is known as the . It is maintained by the (WHATWG), a consortium of the major b ...

HTML5
, is used to display video and audio, primarily using the element, in collaboration with javascript.


History


Development

In 1980,
physicist A physicist is a scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of interest. In classical antiquity, there was no real ancient analog of a modern sci ...

physicist
Tim Berners-Lee Sir Timothy John Berners-Lee (born 8 June 1955), also known as TimBL, is an English computer scientist best known as the inventor of the World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system ...

Tim Berners-Lee
, a contractor at
CERN The European Organization for Nuclear Research (french: Organisation européenne pour la recherche nucléaire), known as CERN (; ; derived from the name ), is a European research organization that operates the largest particle physics laborat ...
, proposed and prototyped
ENQUIRE ENQUIRE was a software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to work. This is in contrast to Computer hardware, physical hardware, from which the system ...
, a system for CERN researchers to use and share documents. In 1989, Berners-Lee wrote a memo proposing an
Internet The Internet (or internet) is the global system of interconnected s that uses the (TCP/IP) to communicate between networks and devices. It is a ' that consists of private, public, academic, business, and government networks of local to ...

Internet
-based
hypertext Douglas Engelbart in 2009, at the 40th anniversary celebrations of "The Mother of All Demos" in San Francisco, a 90-minute 1968 presentation of the NLS (computer system)">NLS computer system which was a combination of hardware and softwar ...

hypertext
system. Berners-Lee specified HTML and wrote the browser and server software in late 1990. That year, Berners-Lee and CERN
data systemsData system is a term used to refer to an organized collection of symbol (formal), symbols and processes that may be used to operate on such symbols. Any organised collection of symbols and symbol-manipulating operations can be considered a data syst ...
engineer
Robert Cailliau Robert Cailliau (born 26 January 1947) is a Belgian informatics engineer, computer scientist A computer scientist is a person A person (plural people or persons) is a being that has certain capacities or attributes such as reason, moralit ...
collaborated on a joint request for funding, but the project was not formally adopted by CERN. In his personal notes from 1990 he listed "some of the many areas in which hypertext is used" and put an
encyclopedia An encyclopedia (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, Amer ...
first. The first publicly available description of HTML was a document calle
"HTML Tags"
first mentioned on the Internet by Tim Berners-Lee in late 1991. It describes 18 elements comprising the initial, relatively simple design of HTML. Except for the hyperlink tag, these were strongly influenced by
SGMLguidSGMLguid, also known as "CERN SGML", "Waterloo based SGML", and "Waterloo SGML", was an early SGML application developed and used at CERN The European Organization for Nuclear Research (french: Organisation européenne pour la recherche nuclé ...
, an in-house
Standard Generalized Markup Language The Standard Generalized Markup Language (SGML; ISO The International Organization for Standardization (ISO; ) is an international standard are technical standards developed by international organizations (intergovernmental organizations), s ...
(SGML)-based documentation format at CERN. Eleven of these elements still exist in HTML 4. HTML is a
markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable from the text, meaning when the document is processed for di ...
that
web browser A web browser (commonly referred to as a browser) is application software Application software (app for short) is computing software designed to carry out a specific task other than one relating to the operation of the computer itself, typical ...

web browser
s use to interpret and compose text, images, and other material into visual or audible web pages. Default characteristics for every item of HTML markup are defined in the browser, and these characteristics can be altered or enhanced by the web page designer's additional use of
CSS #REDIRECT CSS Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation Introduction A presentation conveys information from a speaker to an audience. Presentations are typically demonstrations, intro ...

CSS
. Many of the text elements are found in the 1988 ISO technical report TR 9537 ''Techniques for using SGML'', which in turn covers the features of early text formatting languages such as that used by the RUNOFF command developed in the early 1960s for the CTSS (Compatible Time-Sharing System) operating system: these formatting commands were derived from the commands used by typesetters to manually format documents. However, the SGML concept of generalized markup is based on elements (nested annotated ranges with attributes) rather than merely print effects, with also the separation of structure and markup; HTML has been progressively moved in this direction with CSS. Berners-Lee considered HTML to be an application of SGML. It was formally defined as such by the
Internet Engineering Task Force The Internet Engineering Task Force (IETF) is an open standards organization, which develops and promotes voluntary Internet standards, in particular the technical standards that comprise the Internet protocol suite (TCP/IP). It has no formal ...
(IETF) with the mid-1993 publication of the first proposal for an HTML specification, the "Hypertext Markup Language (HTML)" Internet Draft by Berners-Lee and Dan Connolly, which included an SGML Document type definition to define the grammar. The draft expired after six months, but was notable for its acknowledgment of the
NCSA Mosaic NCSA Mosaic was one of the first web browser A web browser (commonly referred to as a browser) is application software for accessing the World Wide Web upright=1.35, A global map of the web index for countries in 2014 The World Wide ...
browser's custom tag for embedding in-line images, reflecting the IETF's philosophy of basing standards on successful prototypes. Similarly,
Dave Raggett Dave Raggett is an English computer specialist who has played a major role in implementing the World Wide Web upright=1.35, A global map of the web index for countries in 2014 The World Wide Web (WWW), commonly known as the Web, is an inf ...

Dave Raggett
's competing Internet-Draft, "HTML+ (Hypertext Markup Format)", from late 1993, suggested standardizing already-implemented features like tables and fill-out forms. After the HTML and HTML+ drafts expired in early 1994, the IETF created an HTML Working Group, which in 1995 completed "HTML 2.0", the first HTML specification intended to be treated as a standard against which future implementations should be based. Further development under the auspices of the IETF was stalled by competing interests. the HTML specifications have been maintained, with input from commercial software vendors, by the
World Wide Web Consortium The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary ...
(W3C). However, in 2000, HTML also became an international standard (
ISO The International Organization for Standardization (ISO ) is an international standard An international standard is a technical standard A technical standard is an established norm (social), norm or requirement for a repeatable technical task w ...
/
IECIEC may refer to: Businesses and organisations * International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organizati ...
15445:2000). HTML 4.01 was published in late 1999, with further errata published through 2001. In 2004, development began on HTML5 in the
Web Hypertext Application Technology Working Group The Web Hypertext Application Technology Working Group (WHATWG) is a community of people interested in evolving HTML The HyperText Markup Language, or HTML is the standard markup language for documents designed to be displayed in a web br ...
(WHATWG), which became a joint deliverable with the W3C in 2008, and completed and standardized on 28 October 2014.


HTML versions timeline


HTML 2

:; November 24, 1995: HTML 2.0 was published as . Supplemental RFCs added capabilities: ::* November 25, 1995: (form-based file upload) ::* May 1996: (tables) ::* August 1996: (client-side image maps) ::* January 1997: (
internationalization In economics, internationalization or internationalisation is the process of increasing involvement of enterprises in international markets, although there is no agreed definition of internationalization. Internationalization is a crucial strategy ...
)


HTML 3

:; January 14, 1997: HTML 3.2 was published as a
W3C Recommendation The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary f ...
. It was the first version developed and standardized exclusively by the W3C, as the IETF had closed its HTML Working Group on September 12, 1996. ::Initially code-named "Wilbur", HTML 3.2 dropped math formulas entirely, reconciled overlap among various proprietary extensions and adopted most of
Netscape Netscape Communications Corporation (originally Mosaic Communications Corporation) was an American independent computer services company with headquarters in Mountain View, California Mountain View is a city in Santa Clara County, California ...

Netscape
's visual markup tags. Netscape's
blink element The blink element is a non-standard HTML element that indicates to a user agent (generally a web browser) that the page author intends the content of the element to blink (that is, alternate between being visible and invisible). The element was intr ...
and
Microsoft Microsoft Corporation is an American multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body from multiple countries * Multination ...

Microsoft
's
marquee element The marquee tag is a non-standard HTML The HyperText Markup Language, or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) a ...
were omitted due to a mutual agreement between the two companies. A markup for mathematical formulas similar to that in HTML was not standardized until 14 months later in
MathML Mathematical Markup Language (MathML) is a mathematical markup language, an application of XML for describing mathematics, mathematical notations and capturing both its structure and content. It aims at integrating mathematical formulae into Wo ...
.


HTML 4

:; December 18, 1997: HTML 4.0 was published as a W3C Recommendation. It offers three variations: ::* Strict, in which deprecated elements are forbidden ::* Transitional, in which deprecated elements are allowed ::* Frameset, in which mostly only frame related elements are allowed. ::Initially code-named "Cougar", HTML 4.0 adopted many browser-specific element types and attributes, but at the same time sought to phase out Netscape's visual markup features by marking them as
deprecated In several fields, deprecation is the discouragement of use of some terminology, feature, design, or practice, typically because it has been superseded or is no longer considered efficient or safe, without completely removing it or prohibiting its ...
in favor of style sheets. HTML 4 is an SGML application conforming to ISO 8879 – SGML. :; April 24, 1998: HTML 4.0 was reissued with minor edits without incrementing the version number. :; December 24, 1999: HTML 4.01 was published as a W3C Recommendation. It offers the same three variations as HTML 4.0 and its las
errata
were published on May 12, 2001. :; May 2000: ISO/IEC 15445:2000 ("
ISO The International Organization for Standardization (ISO ) is an international standard An international standard is a technical standard A technical standard is an established norm (social), norm or requirement for a repeatable technical task w ...
HTML", based on HTML 4.01 Strict) was published as an ISO/IEC international standard. In the ISO this standard falls in the domain of the
ISO/IEC JTC1/SC34 ISO/IEC JTC 1/SC 34, Document description and processing languages is a subcommittee of the ISO/IEC JTC1 ISO/IEC JTC 1 is a joint technical committee (JTC) of the International Organization for Standardization (ISO) and the International Electrote ...
(ISO/IEC Joint Technical Committee 1, Subcommittee 34 – Document description and processing languages). :: After HTML 4.01, there was no new version of HTML for many years as development of the parallel, XML-based language XHTML occupied the W3C's HTML Working Group through the early and mid-2000s.


HTML 5

:;October 28, 2014: HTML5 was published as a W3C Recommendation. :;November 1, 2016: HTML 5.1 was published as a W3C Recommendation. :;December 14, 2017: HTML 5.2 was published as a W3C Recommendation.


HTML draft version timeline

; October 1991: ''HTML Tags'', an informal CERN document listing 18 HTML tags, was first mentioned in public. ; June 1992: First informal draft of the HTML DTD, with seven See section "Revision History" subsequent revisions (July 15, August 6, August 18, November 17, November 19, November 20, November 22) ; November 1992: HTML DTD 1.1 (the first with a version number, based on RCS revisions, which start with 1.1 rather than 1.0), an informal draft ; June 1993: Hypertext Markup Language was published by the
IETF The Internet Engineering Task Force (IETF) is an open standards organization, which develops and promotes voluntary Internet standards, in particular the technical standards that comprise the Internet protocol suite (TCP/IP). It has no formal ...
IIIR Working Group as an Internet Draft (a rough proposal for a standard). It was replaced by a second version one month later. ; November 1993
HTML+
was published by the IETF as an Internet Draft and was a competing proposal to the Hypertext Markup Language draft. It expired in July 1994. ; November 1994: First draft (revision 00) of HTML 2.0 published by IETF itself (called as "HTML 2.0" from revision 02), that finally led to publication of in November 1995. ; April 1995 (authored March 1995): HTML 3.0 was proposed as a standard to the IETF, but the proposal expired five months later (28 September 1995) without further action. It included many of the capabilities that were in Raggett's HTML+ proposal, such as support for tables, text flow around figures and the display of complex mathematical formulas. :W3C began development of its own Arena browser as a
test bed A testbed (also spelled test bed) is a platform for conducting rigorous, transparent, and replicable testing of scientific theories, computational tools, and new technologies. The term is used across many disciplines to describe experimental resear ...
for HTML 3 and Cascading Style Sheets, but HTML 3.0 did not succeed for several reasons. The draft was considered very large at 150 pages and the pace of browser development, as well as the number of interested parties, had outstripped the resources of the IETF. Browser vendors, including Microsoft and Netscape at the time, chose to implement different subsets of HTML 3's draft features as well as to introduce their own extensions to it. (see
Browser wars A browser war is competition for dominance in the usage share of web browsers. The "First Browser War" during the late 1990s pitted Microsoft's Internet Explorer against Netscape's Netscape Navigator, Navigator. Browser wars continued with the ...
). These included extensions to control stylistic aspects of documents, contrary to the "belief
f the academic engineering community F, or f, is the sixth Letter (alphabet), letter in the English alphabet, modern English alphabet and the ISO basic Latin alphabet. Its name in English is English alphabet#Letter names, ''ef'' (pronounced ), plural ''efs''. History The origin ...
that such things as text color, background texture, font size and font face were definitely outside the scope of a language when their only intent was to specify how a document would be organized." Dave Raggett, who has been a W3C Fellow for many years, has commented for example: "To a certain extent, Microsoft built its business on the Web by extending HTML features." ; January 2008:
HTML5 HTML5 is a used for structuring and presenting content on the . It is the fifth and last major version that is a (W3C) recommendation. The current specification is known as the . It is maintained by the (WHATWG), a consortium of the major b ...

HTML5
was published as a Working Draft by the W3C. :Although its syntax closely resembles that of
SGML The Standard Generalized Markup Language (SGML; ISO The International Organization for Standardization (ISO ) is an international standard An international standard is a technical standard A technical standard is an established norm (social) ...

SGML
,
HTML5 HTML5 is a used for structuring and presenting content on the . It is the fifth and last major version that is a (W3C) recommendation. The current specification is known as the . It is maintained by the (WHATWG), a consortium of the major b ...

HTML5
has abandoned any attempt to be an SGML application and has explicitly defined its own "html" serialization, in addition to an alternative XML-based XHTML5 serialization. ; 2011 HTML5 – Last Call :On 14 February 2011, the W3C extended the charter of its HTML Working Group with clear milestones for HTML5. In May 2011, the working group advanced HTML5 to "Last Call", an invitation to communities inside and outside W3C to confirm the technical soundness of the specification. The W3C developed a comprehensive test suite to achieve broad interoperability for the full specification by 2014, which was the target date for recommendation. In January 2011, the WHATWG renamed its "HTML5" living standard to "HTML". The W3C nevertheless continues its project to release HTML5. ; 2012 HTML5 – Candidate Recommendation :In July 2012, WHATWG and
W3C The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary f ...

W3C
decided on a degree of separation. W3C will continue the HTML5 specification work, focusing on a single definitive standard, which is considered as a "snapshot" by WHATWG. The WHATWG organization will continue its work with HTML5 as a "Living Standard". The concept of a living standard is that it is never complete and is always being updated and improved. New features can be added but functionality will not be removed. :In December 2012, W3C designated HTML5 as a Candidate Recommendation. The criterion for advancement to
W3C Recommendation The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary f ...
is "two 100% complete and fully interoperable implementations". ; 2014 HTML5 – Proposed Recommendation and Recommendation :In September 2014, W3C moved HTML5 to Proposed Recommendation. :On 28 October 2014, HTML5 was released as a stable W3C Recommendation, meaning the specification process is complete.


XHTML versions

XHTML is a separate language that began as a reformulation of HTML 4.01 using
XML Extensible Markup Language (XML) is a markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable fro ...

XML
1.0. It is no longer being developed as a separate standard. * XHTML 1.0 was published as a W3C Recommendation on January 26, 2000, and was later revised and republished on August 1, 2002. It offers the same three variations as HTML 4.0 and 4.01, reformulated in XML, with minor restrictions. * XHTML 1.1 was published as a W3C Recommendation on May 31, 2001. It is based on XHTML 1.0 Strict, but includes minor changes, can be customized, and is reformulated using modules in the W3C recommendation "Modularization of XHTML", which was published on April 10, 2001. * XHTML 2.0 was a working draft, work on it was abandoned in 2009 in favor of work on
HTML5 HTML5 is a used for structuring and presenting content on the . It is the fifth and last major version that is a (W3C) recommendation. The current specification is known as the . It is maintained by the (WHATWG), a consortium of the major b ...

HTML5
and XHTML5. XHTML 2.0 was incompatible with XHTML 1.x and, therefore, would be more accurately characterized as an XHTML-inspired new language than an update to XHTML 1.x. * An XHTML syntax, known as "XHTML5.1", is being defined alongside
HTML5 HTML5 is a used for structuring and presenting content on the . It is the fifth and last major version that is a (W3C) recommendation. The current specification is known as the . It is maintained by the (WHATWG), a consortium of the major b ...

HTML5
in the HTML5 draft.


Transition of HTML Publication to WHATWG

On 28 May 2019, the W3C announced that WHATWG would be the sole publisher of the HTML and DOM standards. The W3C and WHATWG had been publishing competing standards since 2012. While the W3C standard was identical to the WHATWG in 2007 the standards have since progressively diverged due to different design decisions. The WHATWG "Living Standard" had been the de facto web standard for some time.


Markup

HTML markup consists of several key components, including those called ''tags'' (and their ''attributes''), character-based ''data types'', ''character references'' and ''entity references''. HTML tags most commonly come in pairs like and , although some represent ''empty elements'' and so are unpaired, for example . The first tag in such a pair is the ''start tag'', and the second is the ''end tag'' (they are also called ''opening tags'' and ''closing tags''). Another important component is the HTML ''
document type declarationA document type declaration, or DOCTYPE, is an instruction that associates a particular XML or SGML document (for example, a webpage) with a document type definition (DTD) (for example, the formal definition of a particular version of HTML, HTML 2.0 ...
'', which triggers standards mode rendering. The following is an example of the classic "Hello, World!" program: This is a title

Hello world!

The text between and describes the web page, and the text between and is the visible page content. The markup text defines the browser page title shown on browser tabs and
window A window is an opening in a wall A wall is a structure and a surface that defines an area; carries a load; provides , , or ; or, is decorative. There are many kinds of walls, including: * Walls in buildings that form a fundamental part of ...
titles, and the tag defines a division of the page used for easy styling. The Document Type Declaration is for HTML5. If a declaration is not included, various browsers will revert to "
quirks mode In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm of an algorithm (Euclid's algorithm) for calculating the greatest common ...
" for rendering.Activating Browser Modes with Doctype
Hsivonen.iki.fi. Retrieved on 2012-02-16.


Elements

HTML documents imply a structure of nested
HTML element An HTML element is a type of (Hypertext Markup Language) document component, one of several types of HTML nodes (there are also text nodes, comment nodes and others). HTML document is composed of a of simple HTML , such as text nodes, and H ...
s. These are indicated in the document by HTML ''tags'', enclosed in angle brackets thus: . In the simple, general case, the extent of an element is indicated by a pair of tags: a "start tag" and "end tag" . The text content of the element, if any, is placed between these tags. Tags may also enclose further tag markup between the start and end, including a mixture of tags and text. This indicates further (nested) elements, as children of the parent element. The start tag may also include element's ''attributes'' within the tag. These indicate other information, such as identifiers for sections within the document, identifiers used to bind style information to the presentation of the document, and for some tags such as the used to embed images, the reference to the image resource in the format like this: Some elements, such as the line break , or do not permit ''any'' embedded content, either text or further tags. These require only a single empty tag (akin to a start tag) and do not use an end tag. Many tags, particularly the closing end tag for the very commonly used paragraph element , are optional. An HTML browser or other agent can infer the closure for the end of an element from the context and the structural rules defined by the HTML standard. These rules are complex and not widely understood by most HTML coders. The general form of an HTML element is therefore: . Some HTML elements are defined as ''empty elements'' and take the form . Empty elements may enclose no content, for instance, the tag or the inline tag. The name of an HTML element is the name used in the tags. Note that the end tag's name is preceded by a slash character, /, and that in empty elements the end tag is neither required nor allowed. If attributes are not mentioned, default values are used in each case.


Element examples

Header of the HTML document: . The title is included in the head, for example: The Title Headings: HTML headings are defined with the to tags with H1 being the highest (or most important) level and H6 the least:

Heading level 1

Heading level 2

Heading level 3

Heading level 4

Heading level 5
Heading level 6
The effects are:
Heading Level 1
Heading Level 2
Heading Level 3
Heading Level 4
Heading Level 5
Heading Level 6
Note that CSS can drastically change the rendering. Paragraphs:

Paragraph 1

Paragraph 2

Line breaks: . The difference between and is that breaks a line without altering the semantic structure of the page, whereas sections the page into
paragraph A paragraph () is a self-contained unit of discourse in writing Writing is a medium of human communication Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with") is "an apparent answer to the painful d ...
s. The element is an ''empty element'' in that, although it may have attributes, it can take no content and it may not have an end tag.

This
is a paragraph
with
line breaks

This is a link in HTML. To create a link the tag is used. The href attribute holds the
URL A Uniform Resource Locator (URL), colloquially termed a web address, is a reference to a web resource that specifies its location on a computer network A computer network is a group of computers that use a set of common communication prot ...

URL
address of the link. A link to Wikipedia! Inputs: There are many possible ways a user can give input/s like: Comments: Comments can help in the understanding of the markup and do not display in the webpage. There are several types of markup elements used in HTML: ;Structural markup indicates the purpose of text: For example, establishes "Golf" as a second-level heading. Structural markup does not denote any specific rendering, but most web browsers have default styles for element formatting. Content may be further styled using
Cascading Style Sheets #REDIRECT CSS #REDIRECT CSS Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation Introduction A presentation conveys information from a speaker to an audience. Presentations are typically demonst ...

Cascading Style Sheets
(CSS). ;Presentational markup indicates the appearance of the text, regardless of its purpose: For example, indicates that visual output devices should render "boldface" in bold text, but gives little indication what devices that are unable to do this (such as aural devices that read the text aloud) should do. In the case of both and , there are other elements that may have equivalent visual renderings but that are more semantic in nature, such as and respectively. It is easier to see how an aural user agent should interpret the latter two elements. However, they are not equivalent to their presentational counterparts: it would be undesirable for a screen-reader to emphasize the name of a book, for instance, but on a screen such a name would be italicized. Most presentational markup elements have become
deprecated In several fields, deprecation is the discouragement of use of some terminology, feature, design, or practice, typically because it has been superseded or is no longer considered efficient or safe, without completely removing it or prohibiting its ...
under the HTML 4.0 specification in favor of using
CSS #REDIRECT CSS Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation Introduction A presentation conveys information from a speaker to an audience. Presentations are typically demonstrations, intro ...

CSS
for styling. ;Hypertext markup makes parts of a document into links to other documents: An anchor element creates a
hyperlink In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and soft ...

hyperlink
in the document and its href attribute sets the link's target
URL A Uniform Resource Locator (URL), colloquially termed a web address, is a reference to a web resource that specifies its location on a computer network A computer network is a group of computers that use a set of common communication prot ...

URL
. For example, the HTML markup , will render the word "Wikipedia
/span>" as a hyperlink. To render an image as a hyperlink, an img element is inserted as content into the a element. Like br, img is an empty element with attributes but no content or closing tag. .


Attributes

Most of the attributes of an element are name-value pairs, separated by = and written within the start tag of an element after the element's name. The value may be enclosed in single or double quotes, although values consisting of certain characters can be left unquoted in HTML (but not XHTML). Leaving attribute values unquoted is considered unsafe. In contrast with name-value pair attributes, there are some attributes that affect the element simply by their presence in the start tag of the element, like the ismap attribute for the img element. There are several common attributes that may appear in many elements : * The id attribute provides a document-wide unique identifier for an element. This is used to identify the element so that stylesheets can alter its presentational properties, and scripts may alter, animate or delete its contents or presentation. Appended to the URL of the page, it provides a globally unique identifier for the element, typically a sub-section of the page. For example, the ID "Attributes" in https://en.wikipedia.org/wiki/HTML#Attributes. * The class attribute provides a way of classifying similar elements. This can be used for
semantic Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another o ...
or presentation purposes. For example, an HTML document might semantically use the designation to indicate that all elements with this class value are subordinate to the main text of the document. In presentation, 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. Class attributes are used semantically in
microformat Microformats (sometimes abbreviated μF although this conflicts with the SI designation for micro Farad) are a set of defined HTML classes created to serve as consistent and descriptive metadata Metadata is " data" that provides informat ...
s. Multiple class values may be specified; for example puts the element into both the notation and the important classes. * An author may use the style attribute to assign presentational properties to a particular element. It is considered better practice to use an element's id or class attributes to select the element from within a , though sometimes this can be too cumbersome for a simple, specific, or ad hoc styling. * The title attribute is used to attach subtextual explanation to an element. In most
browsers Browse, browser or browsing may refer to: Programs *Web browser, a program used to access the World Wide Web *Code browser, a program for navigating source code *File browser or file manager, a program used to manage files and related objects *Har ...

browsers
this attribute is displayed as a
tooltip The tooltip, also known as infotip or hint, is a common graphical user interface The graphical user interface (GUI "UI" by itself is still usually pronounced . or ) is a form of user interface that allows User (computing), users to Human–co ...

tooltip
. * The lang attribute identifies the natural language of the element's contents, which may be different from that of the rest of the document. For example, in an English-language document:

Oh well, c'est la vie, as they say in France.

The abbreviation element, abbr, can be used to demonstrate some of these attributes: HTML This example displays as HTML; in most browsers, pointing the cursor at the abbreviation should display the title text "Hypertext Markup Language." Most elements take the language-related attribute dir to specify text direction, such as with "rtl" for right-to-left text in, for example,
Arabic Arabic (, ' or , ' or ) is a Semitic language The Semitic languages are a branch of the Afroasiatic language family originating in the Middle East The Middle East is a list of transcontinental countries, transcontinental region ...

Arabic
,
Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, Persian people, the majority ethnic group in Iran, not to be conflated with the Iranian peoples ** Persian language, an Iranian ...
or
Hebrew Hebrew (, , or ) is a Northwest Semitic languages, Northwest Semitic language of the Afroasiatic languages, Afroasiatic language family. Historically, it is regarded as the language of the Israelites, Judeans and their ancestors. It is the o ...
.


Character and entity references

As of version 4.0, HTML defines a set of 252
character entity referenceIn SGML, HTML and XML documents, the logical constructs known as ''character data'' and ''attribute values'' consist of sequences of characters, in which each character can manifest directly (representing itself), or can be represented by a series of ...
s and a set of 1,114,050
numeric character reference A numeric character reference (NCR) is a common markup (computer programming), markup construct used in SGML and SGML-derived markup languages such as HTML and XML. It consists of a short sequence of character (computing), characters that, in turn, ...
s, both of which allow individual characters to be written via simple markup, rather than literally. A literal character and its markup counterpart are considered equivalent and are rendered identically. The ability to " escape" characters in this way allows for the characters < and & (when written as &lt; and &amp;, respectively) to be interpreted as character data, rather than markup. For example, a literal < normally indicates the start of a tag, and & normally indicates the start of a character entity reference or numeric character reference; writing it as &amp; or &#x26; or &#38; allows & to be included in the content of an element or in the value of an attribute. The double-quote character ("), when not used to quote an attribute value, must also be escaped as &quot; or &#x22; or &#34; when it appears within the attribute value itself. Equivalently, the single-quote character ('), when not used to quote an attribute value, must also be escaped as &#x27; or &#39; (or as &apos; in HTML5 or XHTML documents) when it appears within the attribute value itself. If document authors overlook the need to escape such characters, some browsers can be very forgiving and try to use context to guess their intent. The result is still invalid markup, which makes the document less accessible to other browsers and to other
user agent In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm of an algorithm (Euclid's algorithm) for calculating the greatest common ...
s that may try to parse the document for search and indexing purposes for example. Escaping also allows for characters that are not easily typed, or that are not available in the document's
character encoding Character encoding is the process of assigning numbers to graphical Graphics (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country ...
, to be represented within element and attribute content. For example, the acute-accented e (é), a character typically found only on Western European and South American keyboards, can be written in any HTML document as the entity reference &eacute; or as the numeric references &#xE9; or &#233;, using characters that are available on all keyboards and are supported in all character encodings.
Unicode Unicode, formally the Unicode Standard, is an information technology standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requireme ...

Unicode
character encodings such as
UTF-8 UTF-8 is a variable-width character encoding Character encoding is the process of assigning numbers to Graphics, graphical character (computing), characters, especially the written characters of Language, human language, allowing them to be ...
are compatible with all modern browsers and allow direct access to almost all the characters of the world's writing systems.


Data types

HTML defines several
data type In computer science Computer science deals with the theoretical foundations of information, algorithms and the architectures of its computation as well as practical techniques for their application. Computer science is the study of Alg ...
s for element content, such as script data and stylesheet data, and a plethora of types for attribute values, including IDs, names, URIs, numbers, units of length, languages, media descriptors, colors, character encodings, dates and times, and so on. All of these data types are specializations of character data.


Document type declaration

HTML documents are required to start with a
Document Type DeclarationA document type declaration, or DOCTYPE, is an instruction that associates a particular XML or SGML document (for example, a webpage) with a document type definition (DTD) (for example, the formal definition of a particular version of HTML, HTML 2.0 ...
(informally, a "doctype"). In browsers, the doctype helps to define the rendering mode—particularly whether to use
quirks mode In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm of an algorithm (Euclid's algorithm) for calculating the greatest common ...
. The original purpose of the doctype was to enable parsing and validation of HTML documents by SGML tools based on the Document Type Definition (DTD). The DTD to which the DOCTYPE refers contains a machine-readable grammar specifying the permitted and prohibited content for a document conforming to such a DTD. Browsers, on the other hand, do not implement HTML as an application of SGML and by consequence do not read the DTD.
HTML5 HTML5 is a used for structuring and presenting content on the . It is the fifth and last major version that is a (W3C) recommendation. The current specification is known as the . It is maintained by the (WHATWG), a consortium of the major b ...

HTML5
does not define a DTD; therefore, in HTML5 the doctype declaration is simpler and shorter: An example of an HTML 4 doctype This declaration references the DTD for the "strict" version of HTML 4.01. SGML-based validators read the DTD in order to properly parse the document and to perform validation. In modern browsers, a valid doctype activates standards mode as opposed to
quirks mode In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm of an algorithm (Euclid's algorithm) for calculating the greatest common ...
. In addition, HTML 4.01 provides Transitional and Frameset DTDs, as explained below. Transitional type is the most inclusive, incorporating current tags as well as older or "deprecated" tags, with the Strict DTD excluding deprecated tags. Frameset has all tags necessary to make frames on a page along with the tags included in transitional type.


Semantic HTML

Semantic HTML is a way of writing HTML that emphasizes the meaning of the encoded information over its presentation (look). HTML has included semantic markup from its inception, but has also included presentational markup, such as , and tags. There are also the semantically neutral
span and div In HTML, span and div HTML element, tags are elements used to define parts of a Web document, document, so that they are identifiable when a unique classification is necessary. Where other HTML elements such as p (paragraph), em (emphasis), and s ...
tags. Since the late 1990s, when
Cascading Style Sheets #REDIRECT CSS #REDIRECT CSS Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation Introduction A presentation conveys information from a speaker to an audience. Presentations are typically demonst ...

Cascading Style Sheets
were beginning to work in most browsers, web authors have been encouraged to avoid the use of presentational HTML markup with a view to the
separation of presentation and content Separation of content and presentation (or separation of content and style) is the separation of concerns In computer science Computer science deals with the theoretical foundations of information, algorithms and the architectures of its compu ...
. In a 2001 discussion of the
Semantic Web The Semantic Web (sometimes known as Web 3.0) is an extension of the World Wide Web upright=1.35, A global map of the web index for countries in 2014 The World Wide Web (WWW), commonly known as the Web, is an information system where d ...

Semantic Web
,
Tim Berners-Lee Sir Timothy John Berners-Lee (born 8 June 1955), also known as TimBL, is an English computer scientist best known as the inventor of the World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system ...

Tim Berners-Lee
and others gave examples of ways in which intelligent software "agents" may one day automatically crawl the web and find, filter and correlate previously unrelated, published facts for the benefit of human users. Such agents are not commonplace even now, but some of the ideas of
Web 2.0 Web 2.0 (also known as participative (or participatory) web and social web) refers to website A website (also written as web site) is a collection of web page A web page (or webpage) is a hypertext File:Douglas Engelbart in 2008. ...

Web 2.0
, mashups and price comparison websites may be coming close. The main difference between these web application hybrids and Berners-Lee's semantic agents lies in the fact that the current
aggregation Aggregation may refer to: Business and economics * Aggregation problem (economics) * Purchasing aggregation, the joining of multiple purchasers in a group purchasing organization to increase their buying power * Community Choice Aggregation, the jo ...
and hybridization of information is usually designed in by
web developer Web Developer is an Mozilla extension, extension for Mozilla-based web browsers that adds editing and debugging tools for web developers. It has been tested to be compatible with Firefox, Flock (web browser), Flock, and SeaMonkey, Seamonkey. The e ...
s, who already know the web locations and the API semantics of the specific data they wish to mash, compare and combine. An important type of web agent that does crawl and read web pages automatically, without prior knowledge of what it might find, is the
web crawler A Web crawler, sometimes called a spider or spiderbot and often shortened to crawler, is an Internet bot An Internet bot, web Web most often refers to: * Spider web A spider web, spiderweb, spider's web, or cobweb (from the archaic word ...
or search-engine spider. These software agents are dependent on the semantic clarity of web pages they find as they use various techniques and
algorithm In and , an algorithm () is a finite sequence of , computer-implementable instructions, typically to solve a class of problems or to perform a computation. Algorithms are always and are used as specifications for performing s, , , and other ...

algorithm
s to read and index millions of web pages a day and provide web users with search facilities without which the World Wide Web's usefulness would be greatly reduced. In order for search-engine spiders to be able to rate the significance of pieces of text they find in HTML documents, and also for those creating mashups and other hybrids as well as for more automated agents as they are developed, the semantic structures that exist in HTML need to be widely and uniformly applied to bring out the meaning of published text. Presentational markup tags are
deprecated In several fields, deprecation is the discouragement of use of some terminology, feature, design, or practice, typically because it has been superseded or is no longer considered efficient or safe, without completely removing it or prohibiting its ...
in current HTML and
XHTML Extensible HyperText Markup Language (XHTML) is part of the family of XML Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding document A document is a writing, written, drawing, drawn, presented, o ...

XHTML
recommendations. The majority of presentational features from previous versions of HTML are no longer allowed as they lead to poorer accessibility, higher cost of site maintenance, and larger document sizes. Good semantic HTML also improves the
accessibility Accessibility in the sense considered here refers to the design of products, devices, services, or environments so as to be usable by people with disabilities. The concept of accessible design and practice of accessible development ensures b ...

accessibility
of web documents (see also
Web Content Accessibility Guidelines The Web Content Accessibility Guidelines (WCAG) are part of a series of web accessibility guidelines published by the Web Accessibility Initiative (WAI) of the World Wide Web Consortium (W3C), the main international standards organization for the ...
). For example, when a screen reader or audio browser can correctly ascertain the structure of a document, it will not waste the visually impaired user's time by reading out repeated or irrelevant information when it has been marked up correctly.


Delivery

HTML documents can be delivered by the same means as any other computer file. However, they are most often delivered either by
HTTP The Hypertext Transfer Protocol (HTTP) is an application layer An application layer is an abstraction layer that specifies the shared communications protocols and Interface (computing), interface methods used by Host (network), hosts in a c ...
from a
web server A web server is computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets of operations known as Computer program, pr ...
or by
email upThe email_address.html"_;"title="at_sign,_a_part_of_every_SMTP_email_address">at_sign,_a_part_of_every_SMTP_email_address Electronic_mail_(email_or_e-mail)_is_a_method_of_exchanging_messages_("mail")_between_people_using_electronic_dev ...

email
.


HTTP

The
World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system An information system (IS) is a formal, sociotechnical Sociotechnical systems (STS) in organizational development is an approach to complex organizational ...
is composed primarily of HTML documents transmitted from web servers to web browsers using the
Hypertext Transfer Protocol The Hypertext Transfer Protocol (HTTP) is an application layer An application layer is an abstraction layer that specifies the shared communications protocols and Interface (computing), interface methods used by Host (network), hosts in a c ...
(HTTP). However, HTTP is used to serve images, sound, and other content, in addition to HTML. To allow the web browser to know how to handle each document it receives, other information is transmitted along with the document. This
meta data Metadata is "data Data are units of information Information can be thought of as the resolution of uncertainty; it answers the question of "What an entity is" and thus defines both its essence and the nature of its characteristics. T ...
usually includes the
MIME type A media type (formerly known as MIME type) is a two-part identifier for file formats and format contents transmitted on the Internet The Internet (Capitalization of Internet, or internet) is the global system of interconnected computer ...
(e.g., text/html or application/xhtml+xml) and the character encoding (see Character encoding in HTML). In modern browsers, the MIME type that is sent with the HTML document may affect how the document is initially interpreted. A document sent with the XHTML MIME type is expected to be
well-formed Well-formed or wellformed indicate syntactic correctness and may refer to: * Well-formedness, quality of linguistic elements that conform to grammar rules * Well-formed formula, a string that is generated by a formal grammar in logic * Well-formed ...
XML; syntax errors may cause the browser to fail to render it. The same document sent with the HTML MIME type might be displayed successfully, since some browsers are more lenient with HTML. The W3C recommendations state that XHTML 1.0 documents that follow guidelines set forth in the recommendation's Appendix C may be labeled with either MIME Type. XHTML 1.1 also states that XHTML 1.1 documents should be labeled with either MIME type.


HTML e-mail

Most graphical email clients allow the use of a subset of HTML (often ill-defined) to provide formatting and
semantic Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another o ...

semantic
markup not available with
plain text In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and softw ...

plain text
. This may include typographic information like coloured headings, emphasized and quoted text, inline images and diagrams. Many such clients include both a
GUI#REDIRECT graphical user interface The graphical user interface (GUI "UI" by itself is still usually pronounced . or ) is a form of user interface that allows User (computing), users to Human–computer interaction, interact with electronic devic ...
editor for composing HTML e-mail messages and a rendering engine for displaying them. Use of HTML in e-mail is criticized by some because of compatibility issues, because it can help disguise
phishing Phishing is a type of where an attacker sends a fraudulent (e.g., spoofed, fake, or otherwise deceptive) message designed to trick a human victim into revealing to the attacker or to deploy malicious software on the victim's infrastructure l ...

phishing
attacks, because of accessibility issues for blind or visually impaired people, because it can confuse
spam Spam may refer to: * Spam (food) Spam (stylized as SPAM) is a brand of canning, canned cooked pork made by Hormel Foods Corporation. It was introduced by Hormel in 1937 and gained popularity worldwide after its use during World War II. By 2003 ...
filters and because the message size is larger than plain text.


Naming conventions

The most common
filename extension A filename extension, file extension or file type is an identifier specified as a suffix to the name A name is a term used for identification by an external observer. They can identify a class or category of things, or a single thing, either un ...
for
files File or filing may refer to: Mechanical tools and processes * File (tool), used to remove fine amounts of material from a workpiece **Filing (metalworking), a material removal process in manufacturing ** Nail file, a tool used to gently abrade aw ...
containing HTML is .html. A common abbreviation of this is .htm, which originated because some early operating systems and file systems, such as
DOS DOS (, ) is a platform-independent acronym for disk operating system which later became a common shorthand for disk-based operating systems on IBM PC compatible IBM PC compatible computers are similar to the original IBM Personal Computer, IB ...

DOS
and the limitations imposed by
FAT In nutrition Nutrition is the biochemical Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided ...
data structure, limited file extensions to three letters.


HTML Application

An HTML Application (HTA; file extension ".hta") is a
Microsoft Windows Microsoft Windows, commonly referred to as Windows, is a group of several proprietary {{Short pages monitor * *
WHATWG The Web Hypertext Application Technology Working Group (WHATWG) is a community of people interested in evolving HTML The HyperText Markup Language, or HTML is the standard markup language In computer text processing, a markup language ...
'
HTML Living Standard
*
W3C The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary f ...

W3C
'
HTML specification (latest published version)Dave Raggett's Introduction to HTMLTim Berners-Lee Gives the Web a New Definition

HTML Entities
{{DEFAULTSORT:Html Computer-related introductions in 1990 Articles with example code Markup languages Open formats Technical communication
World Wide Web Consortium standards This is a collection of web standards formalized by the World Wide Web Consortium. International standards Standards by organization Web standards World Wide Web Consortium {{CatAutoTOC ...