}} defines a division of the page used for easy styling. Between {{Code||HTML}} and {{Code||HTML}}, a {{Code|
|HTML}} element can be used to define webpage metadata.
[141] =>
[142] => The Document Type Declaration {{code|lang=html|code=}} is for HTML5. If a declaration is not included, various browsers will revert to "[[quirks mode]]" for rendering.
[[http://hsivonen.iki.fi/doctype/ Activating Browser Modes with Doctype]. Hsivonen.iki.fi. Retrieved on 2012-02-16.]
[143] =>
[144] => ===Elements===
[145] => {{Main|HTML element}}
[146] => [[File:HTML element content categories.svg|thumb|HTML element content categories]]
[147] => HTML documents imply a structure of nested [[HTML element]]s. These are indicated in the document by HTML ''tags'', enclosed in angle brackets thus: {{code|lang=html|code=
}}.[{{cite web|title=HTML Elements|url=https://www.w3schools.com/html/html_elements.asp|publisher=w3schools|access-date=16 March 2015}}]{{better source needed|date=February 2019}}
[148] =>
[149] => In the simple, general case, the extent of an element is indicated by a pair of tags: a "start tag" {{code|lang=html|code=
}} and "end tag" {{code|lang=html|code=
}}. The text content of the element, if any, is placed between these tags.
[150] =>
[151] => 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.
[152] =>
[153] => The start tag may also include the 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 {{code|lang=html|code=
}} used to embed images, the reference to the image resource in the format like this: {{code|lang=html|code=
}}
[154] =>
[155] => Some elements, such as the [[line breaking character|line break]] {{code|lang=html|code=
}} 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.
[156] =>
[157] => Many tags, particularly the closing end tag for the very commonly used paragraph element {{code|lang=html|code=
}}, 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 authors.
[158] =>
[159] => The general form of an HTML element is therefore: {{code|lang=html|code=''content'' }}. Some HTML elements are defined as ''empty elements'' and take the form {{code|lang=html|code=}}. Empty elements may enclose no content, for instance, the {{code|lang=html|code=/, and that in empty elements the end tag is neither required nor allowed.
[162] => If attributes are not mentioned, default values are used in each case.
[163] =>
[164] => ====Element examples====
[165] => {{See also|HTML element}}
[166] =>
[167] => Header of the HTML document: {{code|lang=html|code=...}}. The title is included in the head, for example:
[168] =>
[169] =>
[170] => The Title
[171] =>
[174] =>
[175] => ===== Headings =====
[176] => HTML headings are defined with the {{code|lang=html|code=}} to {{code|lang=html|code=}} tags with H1 being the highest (or most important) level and H6 the least:
[177] =>
[178] => Heading level 1
[179] => Heading level 2
[180] => Heading level 3
[181] => Heading level 4
[182] => Heading level 5
[183] => Heading level 6
[184] =>
[185] => The effects are:
[186] =>
[187] => Heading Level 1
[188] => Heading Level 2
[189] => Heading Level 3
[190] => Heading Level 4
[191] => Heading Level 5
[192] => Heading Level 6
[193] =>
[194] =>
[195] => CSS can drastically change the rendering.
[196] => Paragraphs:Paragraph 1
Paragraph 2
}} is that {{code|lang=html|code=
}} sections the page into [[paragraph]]s. The element {{Code|code=This
}} tag is used. The href attribute holds the [[URL]] address of the link.
[203] => A link to Wikipedia!
[207] =>
[211] => {{Anchor|Comments|comments}}'''Comments:'''
[212] => Golf }} establishes "Golf" as a second-level [[HTML element#Basic text|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]] (CSS).[{{cite web|title=CSS Introduction|url=https://www.w3schools.com/css/css_intro.asp|publisher=W3schools|access-date=16 March 2015}}]
[216] => ; Presentational markup indicates the appearance of the text, regardless of its purpose: For example, {{code|lang=html|code=bold text }} indicates that visual output devices should render "boldface" in bold text, but gives a 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 {{code|lang=html|code=bold text }} and {{code|lang=html|code=italic text }}, there are other elements that may have equivalent visual renderings but that are more semantic in nature, such as {{code|lang=html|code=strong text }} and {{code|lang=html|code=emphasized text }} 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 [[Deprecation|deprecated]] under the HTML 4.0 specification in favor of using [[Cascading Style Sheets|CSS]] for styling.
[217] => ;Hypertext markup makes parts of a document into links to other documents: An anchor element creates a [[hyperlink]] in the document and its href attribute sets the link's target [[Uniform Resource Locator|URL]]. For example, the HTML markup {{code|lang=html|code= Wikipedia }}, will render the word "[https://en.wikipedia.org/ Wikipedia] " 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. {{code|lang=html|code== 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).[{{cite web |url=https://www.w3.org/TR/html401/intro/sgmltut.html#h-3.2.2|title=On SGML and HTML|publisher=World Wide Web Consortium|access-date=November 16, 2008}}][{{cite web |url=https://www.w3.org/TR/xhtml1/diffs.html#h-4.4|title=XHTML 1.0 – Differences with HTML 4|publisher=World Wide Web Consortium|access-date=November 16, 2008}}] Leaving attribute values unquoted is considered unsafe.[{{cite web|first=Jukka|last=Korpela|url=https://jkorpela.fi/qattr.html|title=Why attribute values should always be quoted in HTML|publisher=Cs.tut.fi|date=July 6, 1998|access-date=November 16, 2008}}] 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,[{{cite web|title=Tags used in HTML|url=https://www.w3.org/History/19921103-hypertext/hypertext/WWW/MarkUp/Tags.html|date=November 3, 1992|publisher=World Wide Web Consortium|url-status=live|archive-url=https://web.archive.org/web/20100131184344/http://www.w3.org/History/19921103-hypertext/hypertext/WWW/MarkUp/Tags.html|archive-date=January 31, 2010|access-date=November 16, 2008}}] like the ismap attribute for the img element.[{{cite web|url=https://www.w3.org/TR/1999/REC-html401-19991224/struct/objects.html#adef-ismap|title=Objects, Images, and Applets in HTML documents|publisher=World Wide Web Consortium|date=December 24, 1999|access-date=November 16, 2008}}]
[222] =>
[223] => There are several common attributes that may appear in many elements :
[224] =>
[225] => * 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 class attribute provides a way of classifying similar elements. This can be used for [[semantics|semantic]] or presentation purposes. For example, an HTML document might semantically use the designation {{code|lang=html|code=}} 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]]s. Multiple class values may be specified; for example {{code|lang=html|code=}} puts the element into both the notation and the important classes.
[227] => * 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 [[Cascading Style Sheets|stylesheet]], though sometimes this can be too cumbersome for a simple, specific, or ad hoc styling.
[228] => * The title attribute is used to attach a subtextual explanation to an element. In most [[Web browser|browsers]] this attribute is displayed as a [[tooltip]].
[229] => * 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.
abbr, can be used to demonstrate some of these attributes:
[232] =>
[233] => HTML HTML ; in most browsers, pointing the cursor at the abbreviation should display the title text "Hypertext Markup Language."
[236] =>
[237] => 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 language|Arabic]], [[Persian language|Persian]] or [[Hebrew language|Hebrew]].[{{cite web|title=H56: Using the dir attribute on an inline element to resolve problems with nested directional runs|url=https://www.w3.org/TR/WCAG-TECHS/H56.html|website=Techniques for WCAG 2.0|publisher=W3C|access-date=18 September 2010}}]
[238] =>
[239] => ===Character and entity references===
[240] => {{See also|List of XML and HTML character entity references|Unicode and HTML}}
[241] =>
[242] => As of version 4.0, HTML defines a set of 252 [[character entity reference]]s and a set of 1,114,050 [[numeric character reference]]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.
[243] =>
[244] => The ability to "[[escape character|escape]]" characters in this way allows for the characters < and & (when written as < and &, 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 & or & or & 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 " or " or " 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 ' or ' (or as ' in HTML5 or XHTML documents[{{cite web|url=https://dev.w3.org/html5/html-author/charref|title=Character Entity Reference Chart|publisher=World Wide Web Consortium|date=October 24, 2012}}][{{cite web|url=https://www.w3.org/TR/xhtml1/#C_16|title=The Named Character Reference '|publisher=World Wide Web Consortium|date=January 26, 2000}}]) 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]]s that may try to parse the document for [[Web crawler|search and indexing]] purposes for example.
[245] =>
[246] => Escaping also allows for characters that are not easily typed, or that are not available in the document's [[character encoding]], to be represented within the 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 é or as the numeric references é or é, using characters that are available on all keyboards and are supported in all character encodings. [[Unicode]] character encodings such as [[UTF-8]] are compatible with all modern browsers and allow direct access to almost all the characters of the world's writing systems.[{{cite web|title=''The Unicode Standard'': A Technical Introduction |publisher=Unicode |url=https://www.unicode.org/standard/principles.html|access-date=2010-03-16}}]
[247] => {| class="wikitable"
[248] => |+Example HTML Escape Sequences
[249] => !Named
[250] => !Decimal
[251] => !Hexadecimal
[252] => !Result
[253] => !Description
[254] => !Notes
[255] => |-
[256] => |{{Code|code=&}}
[257] => |{{Code|code=&}}
[258] => |{{Code|code=&}}
[259] => |{{Code|code=&}}
[260] => |[[Ampersand]]
[261] => |
[262] => |-
[263] => |{{Code|code=<}}
[264] => |{{Code|code=<}}
[265] => |{{Code|code=<}}
[266] => |{{Code|code=<}}
[267] => |[[Less-than sign|Less Than]]
[268] => |
[269] => |-
[270] => |{{Code|code=>}}
[271] => |{{Code|code=>}}
[272] => |{{Code|code=>}}
[273] => |{{Code|code=>}}
[274] => |[[Greater-than sign|Greater Than]]
[275] => |
[276] => |-
[277] => |{{Code|code="}}
[278] => |{{Code|code="}}
[279] => |{{Code|code="}}
[280] => |{{Code|code="}}
[281] => |[[Double quote|Double Quote]]
[282] => |
[283] => |-
[284] => |{{Code|code='}}
[285] => |{{Code|code='}}
[286] => |{{Code|code='}}
[287] => |{{Code|code='}}
[288] => |[[Single quote|Single Quote]]
[289] => |
[290] => |-
[291] => |{{Code|code= }}
[292] => |{{Code|code= }}
[293] => |{{Code|code= }}
[294] => |{{Code|code=}}
[295] => |[[Non-breaking space|Non-Breaking Space]]
[296] => |
[297] => |-
[298] => |{{Code|code=©}}
[299] => |{{Code|code=©}}
[300] => |{{Code|code=©}}
[301] => |{{Code|code=©}}
[302] => |[[Copyright symbol|Copyright]]
[303] => |
[304] => |-
[305] => |{{Code|code=®}}
[306] => |{{Code|code=®}}
[307] => |{{Code|code=®}}
[308] => |{{Code|code=®}}
[309] => |[[Registered trademark symbol|Registered Trademark]]
[310] => |
[311] => |-
[312] => |{{Code|code=†}}
[313] => |{{Code|code=†}}
[314] => |{{Code|code=†}}
[315] => |{{Code|code=†}}
[316] => | [[Dagger (mark)|Dagger]]
[317] => |
[318] => |-
[319] => |{{Code|code=‡}}
[320] => |{{Code|code=‡}}
[321] => |{{Code|code=‡}}
[322] => |{{Code|code=‡}}
[323] => | [[Dagger (mark)|Double dagger]]
[324] => | Names are case sensitive
[325] => |-
[326] => |{{Code|code=‡}}
[327] => |{{Code|code=‡}}
[328] => |{{Code|code=‡}}
[329] => |{{Code|code=‡}}
[330] => | [[Dagger (mark)|Double dagger]]
[331] => | Names may have synonyms
[332] => |-
[333] => |{{Code|code=™}}
[334] => |{{Code|code=™}}
[335] => |{{Code|code=™}}
[336] => |{{Code|code=™}}
[337] => |[[Trademark symbol|Trademark]]
[338] => |
[339] => |}
[340] =>
[341] => ===Data types===
[342] => HTML defines several [[data type]]s for element content, such as script data and stylesheet data, and a plethora of types for attribute values, including IDs, names, [[Uniform Resource Identifier|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.
[343] =>
[344] => ===Document type declaration===
[345] => HTML documents are required to start with a [[Document Type Declaration]] (informally, a "doctype"). In browsers, the doctype helps to define the rendering mode—particularly whether to use [[quirks mode]].
[346] =>
[347] => The original purpose of the doctype was to enable the 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 as consequence do not read the DTD.
[348] =>
[349] => [[HTML5]] does not define a DTD; therefore, in HTML5 the doctype declaration is simpler and shorter:[{{cite web |url=https://www.w3.org/TR/html/syntax.html#doctype-syntax |access-date=2013-08-19 |title=The HTML syntax |work=HTML Standard }}]
[350] =>
[351] =>
[352] =>
[353] =>
[354] =>
[355] => An example of an HTML 4 doctype
[356] =>
[357] =>
[358] =>
[359] =>
[360] =>
[361] => 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]].
[362] =>
[363] => In addition, HTML 4.01 provides Transitional and Frameset DTDs, [[#Transitional versus strict|as explained below]]. The transitional type is the most inclusive, incorporating current tags as well as older or "deprecated" tags, with the Strict DTD excluding deprecated tags. The frameset has all tags necessary to make frames on a page along with the tags included in transitional type.[{{Cite web|title=HTML 4 Frameset Document Type Definition|url=https://www.w3.org/TR/html401/sgml/framesetdtd.html|access-date=2021-12-25|website=W3C}}]
[364] =>
[365] => ==Semantic HTML==
[366] => {{Main|Semantic HTML}}
[367] => 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,[{{cite book|last1=Berners-Lee|first1=Tim|last2=Fischetti|first2=Mark|title=Weaving the Web: The Original Design and Ultimate Destiny of the World Wide Web by Its Inventor|url=https://archive.org/details/weavingweborigin00bern_0|url-access=registration|isbn=978-0-06-251587-2|publisher=Harper|location=San Francisco|year=2000}}] but has also included presentational markup, such as {{code|lang=html|code=}}, {{code|lang=html|code=}} and {{code|lang=html|code= }} tags. There are also the semantically neutral [[div and span]] tags. Since the late 1990s, when [[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 content and presentation]].[{{cite web|url=https://www.w3.org/MarkUp/Guide/Style.html|title=Adding a touch of style|last=Raggett|first=Dave|year=2002|publisher=W3C|access-date=October 2, 2009}} This article notes that presentational HTML markup may be useful when targeting browsers "before Netscape 4.0 and Internet Explorer 4.0". See the [[list of web browsers]] to confirm that these were both released in 1997.]
[368] =>
[369] => In a 2001 discussion of the [[Semantic Web]], [[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.[{{cite magazine |author=Berners-Lee |first1=Tim |last2=Hendler |first2=James |last3=Lassila |first3=Ora |date=May 1, 2001 |title=The Semantic Web |url=http://www.scientificamerican.com/article.cfm?id=the-semantic-web |magazine=Scientific American |access-date=October 2, 2009}}] Such agents are not commonplace even now, but some of the ideas of [[Web 2.0]], [[Mashup (web application hybrid)|mashups]] and [[Price comparison service|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 [[Feed aggregator|aggregation]] and hybridization of information is usually designed by [[web developer]]s, who already know the web locations and the [[Application programming interface|API semantics]] of the specific data they wish to mash, compare and combine.
[370] =>
[371] => 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]] 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]]s to read and index millions of web pages a day and provide web users with [[Web search engine|search facilities]] without which the World Wide Web's usefulness would be greatly reduced.
[372] =>
[373] => 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 the published text.[{{cite web|url=http://eprints.ecs.soton.ac.uk/12614/1/Semantic_Web_Revisted.pdf|title=The Semantic Web Revisited|author=Nigel Shadbolt, Wendy Hall and Tim Berners-Lee|publisher=IEEE Intelligent Systems|year=2006|access-date=October 2, 2009|archive-date=March 20, 2013|archive-url=https://web.archive.org/web/20130320130521/http://eprints.soton.ac.uk/262614/1/Semantic_Web_Revisted.pdf|url-status=dead}}]
[374] =>
[375] => Presentational markup tags are [[deprecation|deprecated]] in current HTML and [[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.[{{cite web |title=HTML: The Living Standard |url=https://html.spec.whatwg.org/dev/introduction.html#restrictions-on-content-models-and-on-attribute-values |website=WHATWG |access-date=27 September 2018}}]
[376] =>
[377] => Good semantic HTML also improves the [[accessibility]] of web documents (see also [[Web Content Accessibility Guidelines]]). 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.
[378] =>
[379] => ==Delivery==
[380] => HTML documents can be delivered by the same means as any other computer file. However, they are most often delivered either by [[Hypertext Transfer Protocol|HTTP]] from a [[web server]] or by [[email]].
[381] =>
[382] => ===HTTP===
[383] => {{Main|Hypertext Transfer Protocol}}
[384] => The [[World Wide Web]] is composed primarily of HTML documents transmitted from web servers to web browsers using the [[Hypertext Transfer Protocol]] (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]] usually includes the [[MIME type]] (e.g., text/html or application/xhtml+xml ) and the character encoding (see [[Character encoding in HTML]]).
[385] =>
[386] => 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 document|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.
[387] =>
[388] => 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.[{{cite web|url=https://www.w3.org/TR/xhtml1/#media|title=XHTML 1.0 The Extensible HyperText Markup Language (Second Edition)|publisher=World Wide Web Consortium|orig-date=2000|year=2002|access-date=December 7, 2008|quote=XHTML Documents which follow the guidelines set forth in Appendix C, "HTML Compatibility Guidelines" may be labeled with the Internet Media Type "text/html" [RFC2854], as they are compatible with most HTML browsers. Those documents, and any other document conforming to this specification, may also be labeled with the Internet Media Type "application/xhtml+xml" as defined in [RFC3236].}}] XHTML 1.1 also states that XHTML 1.1 documents should[{{cite journal |url=http://www.ietf.org/rfc/rfc2119.txt|title=Key words for use in RFCs to Indicate Requirement Levels|website=Internet Engineering Task Force |year=1997|access-date=December 7, 2008|rfc=2119|quote=3. SHOULD This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.|last1=Bradner|first1=Scott O.|doi=10.17487/RFC2119 }}] be labeled with either MIME type.[{{cite web|url=https://www.w3.org/TR/xhtml11/conformance.html#strict|title=XHTML 1.1 – Module-based XHTML — Second Edition|publisher=World Wide Web Consortium|year=2007|access-date=December 7, 2008|quote=XHTML 1.1 documents SHOULD be labeled with the Internet Media Type text/html as defined in [RFC2854] or application/xhtml+xml as defined in [RFC3236].}}]
[389] =>
[390] => ===HTML e-mail===
[391] => {{Main|HTML email}}
[392] => Most graphical email clients allow the use of a subset of HTML (often ill-defined) to provide formatting and [[semantic web|semantic]] markup not available with [[plain text]]. This may include typographic information like colored headings, emphasized and quoted text, inline images and diagrams. Many such clients include both a [[Graphical user interface|GUI]] 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]] attacks, because of accessibility issues for blind or visually impaired people, because it can confuse [[Email spam|spam]] filters and because the message size is larger than plain text.
[393] =>
[394] => ===Naming conventions===
[395] => The most common [[filename extension]] for [[computer file|files]] containing HTML is .html . A common abbreviation of this is .htm , which originated because some early operating systems and file systems, such as [[DOS]] and the limitations imposed by [[File Allocation Table|FAT]] data structure, limited file extensions to [[8.3 filename|three letters]].[{{cite web|title=Naming Files, Paths, and Namespaces|url=https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396|publisher=Microsoft|access-date=16 March 2015}}]
[396] =>
[397] => ===HTML Application===
[398] => {{Main|HTML Application}}
[399] => An HTML Application (HTA; file extension .hta ) is a [[Microsoft Windows]] application that uses HTML and Dynamic HTML in a [[Web browser|browser]] to provide the application's graphical interface. A regular HTML file is confined to the security model of the [[Browser security|web browser's security]], communicating only to web servers and manipulating only web page objects and [[HTTP cookie|site cookies]]. An HTA runs as a fully trusted application and therefore has more privileges, like creation/editing/removal of files and [[Windows Registry]] entries. Because they operate outside the browser's security model, HTAs cannot be executed via HTTP, but must be downloaded (just like an [[EXE|EXE file]]) and executed from local file system.
[400] =>
[401] => ==HTML4 variations==
[402] => Since its inception, HTML and its associated protocols gained acceptance relatively quickly. However, no clear standards existed in the early years of the language. Though its creators originally conceived of HTML as a semantic language devoid of presentation details,[[https://www.w3.org/History/19921103-hypertext/hypertext/WWW/MarkUp/HTMLConstraints.html HTML Design Constraints], W3C Archives] practical uses pushed many presentational elements and attributes into the language, driven largely by the various browser vendors. The latest standards surrounding HTML reflect efforts to overcome the sometimes chaotic development of the language[[http://ei.cs.vt.edu/~wwwbtb/book/chap13/who.html WWW: BTB – HTML], Pris Sears] and to create a rational foundation for building both meaningful and well-presented documents. To return HTML to its role as a semantic language, the [[World Wide Web Consortium|W3C]] has developed style languages such as [[Cascading Style Sheets|CSS]] and [[XSL]] to shoulder the burden of presentation. In conjunction, the HTML specification has slowly reined in the presentational elements.
[403] =>
[404] => There are two axes differentiating various variations of HTML as currently specified: SGML-based HTML versus XML-based HTML (referred to as XHTML) on one axis, and strict versus transitional (loose) versus frameset on the other axis.
[405] =>
[406] => ===SGML-based versus XML-based HTML===
[407] => One difference in the latest{{when|date=March 2022}} HTML specifications lies in the distinction between the SGML-based specification and the XML-based specification. The XML-based specification is usually called [[XHTML]] to distinguish it clearly from the more traditional definition. However, the root element name continues to be "html" even in the XHTML-specified HTML. The W3C intended XHTML 1.0 to be identical to HTML 4.01 except where limitations of XML over the more complex SGML require workarounds. Because XHTML and HTML are closely related, they are sometimes documented in parallel. In such circumstances, some authors [[(X)HTML|conflate the two names]] as (X)HTML or X(HTML).
[408] =>
[409] => Like HTML 4.01, XHTML 1.0 has three sub-specifications: strict, transitional, and frameset.
[410] =>
[411] => Aside from the different opening declarations for a document, the differences between an HTML 4.01 and XHTML 1.0 document—in each of the corresponding DTDs—are largely syntactic. The underlying syntax of HTML allows many shortcuts that XHTML does not, such as elements with optional opening or closing tags, and even empty elements which must not have an end tag. By contrast, XHTML requires all elements to have an opening tag and a closing tag. XHTML, however, also introduces a new shortcut: an XHTML tag may be opened and closed within the same tag, by including a slash before the end of the tag like this: {{code|lang=html|code=[Freeman, E (2005). Head First HTML. O'Reilly.]
[412] =>
[413] => To understand the subtle differences between HTML and XHTML, consider the transformation of a valid and well-formed XHTML 1.0 document that adheres to Appendix C (see below) into a valid HTML 4.01 document. Making this translation requires the following steps:
[414] => # '''The language for an element should be specified with a lang attribute rather than the XHTML xml:lang attribute.''' XHTML uses XML's built-in language-defining functionality attribute.
[415] => # '''Remove the XML namespace (xmlns=URI).''' HTML has no facilities for namespaces.
[416] => # '''Change the document type declaration''' from XHTML 1.0 to HTML 4.01. (see [[#Document type declaration|DTD section]] for further explanation).
[417] => # If present, '''remove the XML declaration.''' (Typically this is: {{code|lang=xml|code=}}).
[418] => # '''Ensure that the document's MIME type is set to text/html.''' For both HTML and XHTML, this comes from the HTTP Content-Type header sent by the server.
[419] => # '''Change the XML empty-element syntax to an HTML style empty element''' ({{code|lang=html|code=xml:lang and lang attributes on any elements assigning language.
[427] => * Use the empty-element syntax only for elements specified as empty in HTML.
[428] => * Include an extra space in empty-element tags: for example {{code|lang=html|code=
}}, not {{code|lang=html|code=
}}).
[430] => * Omit the XML declaration.
[431] =>
[432] => By carefully following the W3C's compatibility guidelines, a user agent should be able to interpret the document equally as HTML or XHTML. For documents that are XHTML 1.0 and have been made compatible in this way, the W3C permits them to be served either as HTML (with a text/html [[MIME type]]), or as XHTML (with an application/xhtml+xml or application/xml MIME type). When delivered as XHTML, browsers should use an XML parser, which adheres strictly to the XML specifications for parsing the document's contents.
[433] =>
[434] => ===Transitional versus strict===
[435] => HTML 4 defined three different versions of the language: Strict, Transitional (once called Loose), and Frameset. The Strict version is intended for new documents and is considered best practice, while the Transitional and Frameset versions were developed to make it easier to transition documents that conformed to older HTML specifications or did not conform to any specification to a version of HTML 4. The Transitional and Frameset versions allow for presentational markup, which is omitted in the Strict version. Instead, [[cascading style sheets]] are encouraged to improve the presentation of HTML documents. Because XHTML 1 only defines an XML syntax for the language defined by HTML 4, the same differences apply to XHTML 1 as well.
[436] =>
[437] => The Transitional version allows the following parts of the vocabulary, which are not included in the Strict version:
[438] => * '''A looser content model'''
[439] => ** Inline elements and plain text are allowed directly in: body, blockquote, form, noscript and noframes
[440] => * '''Presentation related elements'''
[441] => ** underline (u)(Deprecated. can confuse a visitor with a hyperlink.)
[442] => ** strike-through (s)
[443] => ** center (Deprecated. use CSS instead.)
[444] => ** font (Deprecated. use CSS instead.)
[445] => ** basefont (Deprecated. use CSS instead.)
[446] => * '''Presentation related attributes'''
[447] => ** background (Deprecated. use CSS instead.) and bgcolor (Deprecated. use CSS instead.) attributes for body (required element according to the W3C.) element.
[448] => ** align (Deprecated. use CSS instead.) attribute on div, form, paragraph (p) and heading (h1...h6) elements
[449] => ** align (Deprecated. use CSS instead.), noshade (Deprecated. use CSS instead.), size (Deprecated. use CSS instead.) and width (Deprecated. use CSS instead.) attributes on hr element
[450] => ** align (Deprecated. use CSS instead.), border, vspace and hspace attributes on img and object (caution: the object element is only supported in Internet Explorer (from the major browsers)) elements
[451] => ** align (Deprecated. use CSS instead.) attribute on legend and caption elements
[452] => ** align (Deprecated. use CSS instead.) and bgcolor (Deprecated. use CSS instead.) on table element
[453] => ** nowrap (Obsolete), bgcolor (Deprecated. use CSS instead.), width, height on td and th elements
[454] => ** bgcolor (Deprecated. use CSS instead.) attribute on tr element
[455] => ** clear (Obsolete) attribute on br element
[456] => ** compact attribute on dl, dir and menu elements
[457] => ** type (Deprecated. use CSS instead.), compact (Deprecated. use CSS instead.) and start (Deprecated. use CSS instead.) attributes on ol and ul elements
[458] => ** type and value attributes on li element
[459] => ** width attribute on pre element
[460] => * '''Additional elements in Transitional specification'''
[461] => ** menu (Deprecated. use CSS instead.) list (no substitute, though the unordered list, is recommended)
[462] => ** dir (Deprecated. use CSS instead.) list (no substitute, though the unordered list is recommended)
[463] => ** isindex (Deprecated.) (element requires server-side support and is typically added to documents server-side, form and input elements can be used as a substitute)
[464] => ** applet (Deprecated. use the object element instead.)
[465] => * '''The language (Obsolete) attribute on script element''' (redundant with the type attribute).
[466] => * '''Frame related entities'''
[467] => ** iframe
[468] => ** noframes
[469] => ** target (Deprecated in the map, link and form elements.) attribute on a, client-side image-map (map), link, form and base elements
[470] =>
[471] => The Frameset version includes everything in the Transitional version, as well as the frameset element (used instead of body) and the frame element.
[472] =>
[473] => ===Frameset versus transitional===
[474] => In addition to the above transitional differences, the frameset specifications (whether XHTML 1.0 or HTML 4.01) specify a different content model, with frameset replacing body, that contains either frame elements, or optionally noframes with a body.
[475] =>
[476] => ===Summary of specification versions===
[477] => As this list demonstrates, the loose versions of the specification are maintained for legacy support. However, contrary to popular misconceptions, the move to XHTML does not imply a removal of this legacy support. Rather the X in XML stands for extensible and the W3C is modularizing the entire specification and opens it up to independent extensions. The primary achievement in the move from XHTML 1.0 to XHTML 1.1 is the modularization of the entire specification. The strict version of HTML is deployed in XHTML 1.1 through a set of modular extensions to the base XHTML 1.1 specification. Likewise, someone looking for the loose (transitional) or frameset specifications will find similar extended XHTML 1.1 support (much of it is contained in the legacy or frame modules). Modularization also allows for separate features to develop on their own timetable. So for example, XHTML 1.1 will allow quicker migration to emerging XML standards such as [[MathML]] (a presentational and semantic math language based on XML) and [[XForms]]—a new highly advanced web-form technology to replace the existing HTML forms.
[478] =>
[479] => In summary, the HTML 4 specification primarily reined in all the various HTML implementations into a single clearly written specification based on SGML. XHTML 1.0, ported this specification, as is, to the new XML-defined specification. Next, XHTML 1.1 takes advantage of the extensible nature of XML and modularizes the whole specification. XHTML 2.0 was intended to be the first step in adding new features to the specification in a standards-body-based approach.
[480] =>
[481] => ==WHATWG HTML versus HTML5==
[482] => {{Main|#Transition of HTML Publication to WHATWG}}
[483] => The HTML Living Standard, which is developed by WHATWG, is the official version, while W3C HTML5 is no longer separate from WHATWG.
[484] =>
[485] => ==WYSIWYG editors==
[486] => {{missing information|contenteditable|date=January 2021}}
[487] => There are some [[WYSIWYG]] editors (What You See Is What You Get), in which the user lays out everything as it is to appear in the HTML document using a [[graphical user interface]] (GUI), often similar to [[word processor]]s. The editor renders the document rather than showing the code, so authors do not require extensive knowledge of HTML.
[488] =>
[489] => The WYSIWYG editing model has been criticized,[Sauer, C.: WYSIWIKI – Questioning WYSIWYG in the Internet Age. In: Wikimania (2006)][Spiesser, J., Kitchen, L.: Optimization of HTML automatically generated by WYSIWYG programs. In: 13th International Conference on World Wide Web, pp. 355—364. WWW '04. ACM, New York, NY (New York, NY, U.S., May 17–20, 2004)] primarily because of the low quality of the generated code; there are voices{{who|date=June 2020}} advocating a change to the [[WYSIWYM]] model (What You See Is What You Mean).
[490] =>
[491] => WYSIWYG editors remain a controversial topic because of their perceived flaws such as:
[492] =>
[493] => * Relying mainly on the layout as opposed to meaning, often using markup that does not convey the intended meaning but simply copies the layout.[[http://xhtml.com/en/xhtml/reference/blockquote/ XHTML Reference: blockquote] {{Webarchive|url=https://web.archive.org/web/20100325160356/http://xhtml.com/en/xhtml/reference/blockquote/ |date=2010-03-25 }}. Xhtml.com. Retrieved on 2012-02-16.]
[494] => * Often producing extremely verbose and redundant code that fails to make use of the cascading nature of HTML and [[CSS]].
[495] => * Often producing ungrammatical markup, called [[tag soup]] or semantically incorrect markup (such as {{code|lang=html|code=}} for italics).
[496] => * As a great deal of the information in HTML documents is not in the layout, the model has been criticized for its "what you see is all you get"-nature.[[http://www.invisiblerevolution.net/ Doug Engelbart's INVISIBLE REVOLUTION]. Invisiblerevolution.net. Retrieved on 2012-02-16.]
[497] =>
[498] => ==See also==
[499] =>
[500] => {{div col|colwidth=20em}}
[501] => * [[Breadcrumb navigation]]
[502] => * [[Comparison of HTML parsers]]
[503] => * [[Dynamic web page]]
[504] => * [[HTML character references]]
[505] => * [[List of document markup languages]]
[506] => * [[List of XML and HTML character entity references]]
[507] => * [[Microdata (HTML)]]
[508] => * [[Microformat]]
[509] => * [[Polyglot markup]]
[510] => * [[Semantic HTML]]
[511] => * [[W3C Markup Validation Service|W3C (X)HTML Validator]]
[512] => * [[Web colors]]
[513] => {{div col end}}
[514] =>
[515] => ==References==
[516] => {{reflist|30em}}
[517] =>
[518] => ==External links==
[519] => {{wikibooks}}
[520] =>
[521] => {{sister project links|d=Q8811|c=category:HTML|b=HyperText Markup Language|v=HTML|n=no|q=no|s=no|wikt=HTML|m=Help:HTML in wikitext|mw=HTML restriction|species=no}}
[522] => *{{Curlie|Computers/Data_Formats/Markup_Languages/HTML/Reference/}}
[523] => *[[WHATWG]]'s [https://html.spec.whatwg.org/multipage/ HTML Living Standard]
[524] => *[https://www.w3.org/MarkUp/Guide/ Dave Raggett's Introduction to HTML]
[525] => *[https://web.archive.org/web/20110412130543/http://computemagazine.com/man-who-invented-world-wide-web-gives-new-definition Tim Berners-Lee Gives the Web a New Definition] (archived 12 April 2011)
[526] => * [https://meiert.com/en/indices/html-elements/ List of all HTML elements from all major versions]
[527] => * [https://www.w3schools.com/html/html_entities.asp HTML Entities]
[528] => * {{Cite web |author=Sean B. Palmer |title=Early History of HTML – 1990 to 1992 |url=http://infomesh.net/html/history/early/ |access-date=2022-04-13 |website=Infomesh}} (Timeframe: 1980–1995)
[529] =>
[530] => {{Web browsers|fsp}}
[531] => {{W3C standards}}
[532] => {{Document markup languages}}
[533] => {{ISO standards}}
[534] => {{List of International Electrotechnical Commission standards}}
[535] => {{Authority control}}
[536] => {{Portal bar|Computer programming}}
[537] =>
[538] => {{DEFAULTSORT:Html}}
[539] => [[Category:HTML| ]]
[540] => [[Category:Computer-related introductions in 1990]]
[541] => [[Category:Articles with example code]]
[542] => [[Category:Markup languages]]
[543] => [[Category:Open formats]]
[544] => [[Category:Technical communication]]
[545] => [[Category:World Wide Web Consortium standards]]
[546] => [[Category:SGML]]
[] =>
)
good wiki
HTML
HTML (Hypertext Markup Language) is the standard markup language for creating web pages and applications. It is a fundamental technology used to structure and present content on the World Wide Web.
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About
It is a fundamental technology used to structure and present content on the World Wide Web. HTML is composed of a series of elements, which are represented by tags, and it allows users to build the structure of a web page by defining headings, paragraphs, lists, images, links, and more.
Commonly referred to as the backbone of the internet, HTML provides a standardized way of organizing content, making it accessible and readable by web browsers. This markup language is designed to be easy to understand and learn, making it accessible to both beginners and experienced developers.
The evolution of HTML has led to various versions, with HTML5 being the most recent and widely used. HTML5 introduced several advanced features and functionalities, including support for multimedia elements (such as audio and video), canvas for rendering graphics, enhanced form controls, and more.
The HTML page structure is built using a combination of tags, attributes, and values, which define the appearance and behavior of the content. Tags are enclosed in angle brackets (< >) and, with the use of attributes, determine how the content is displayed. Commonly used tags include heading tags (h1 to h6), paragraph tags (p), anchor tags (a) for creating links, image tags (img) for inserting images, and list tags (ul, ol, li) for creating lists.
HTML allows for the separation of content and design through the use of cascading style sheets (CSS). CSS is used to define the visual presentation of HTML elements by specifying colors, fonts, layouts, and other stylistic properties.
The HTML specification is maintained and developed by the World Wide Web Consortium (W3C) to ensure compatibility and interoperability among various web browsers. The versatility and simplicity of HTML have made it a fundamental technology for web development, catering to a wide range of platforms and devices.
In conclusion, HTML is a markup language that forms the foundation of web pages and applications. It provides a structured way to organize and present content, and it has evolved over the years to encompass advanced features and functionalities. HTML, along with CSS and other web technologies, plays a crucial role in creating immersive and interactive web experiences.
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