HTML

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HyperText Markup Language (HTML) is a markup language designed for the creation of web pages and other information viewable in a browser. Originally defined as a simple application of SGML, which is used by organizations with complex publishing requirements, HTML is now an Internet standard maintained mainly by the World Wide Web Consortium (W3C).

The most recent version of HTML is HTML 4.01, although it has been since superseded by XHTML.

Contents

1 Introduction

2 Markup

3 Separation of style and content

3.1 The document type definition (DTD)

4 Version history of the standard

5 See also

6 External links

Introduction

HTML is a form of markup which is used to instruct the browser to display more complex results when viewed in a web browser. The markup is usually stored in a text file ending in an alternate extension of .txt such as .html or .htm. Usually the files are created to be accesed over the world wide web, which uses the HTTP network protocol to transfer the files to requesting computers. When a HTML file transfer is complete it is then rendered by a internet browser such as Mozilla Firefox or Microsoft Internet Explorer in order to be displayed to the user. HTML can also be rendered by applications such as email programs or cellphones that have web browsing capabilitys.

Markup

There are four kinds of markup elements in HTML:

structural markup that describes the purpose of text (for example, <h1>Golf</h1> will cause the browser to render "Golf" as a first–level heading (such as how "Markup" above is rendered),
presentational markup that describes the visual appearance of text regardless of its function (for example, <b>boldface</b> will render bold text. Presentational markup has since been superceded by CSS and is therefor no longer recommended for presentational purposes,
hypertext markup which links parts of the document to other documents (for example, <a href="http://www.wikipedia.org/">Wikipedia</a> will render the word Wikipedia as a hyperlink to the specified URL), and
widget elements that create objects (for example, buttons and lists).

Note that, besides the presentational markup, the markup itself does not determine how the content within that markup will look. All of the non-presentational markups listed above tell the browser what object to render or function to perform. Cascading Style Sheets are usually used to specify the style of the text or content.

Separation of style and content

Efforts of the web development community have led to a new thinking in the way a web document should be written; XHTML epitomizes this effort. Standards stress using markup which suggests the structure of the document, like headings, paragraphs, block quoted text, and tables, instead of using markup which is written for visual purposes only, like <font>, <b> (bold), and <i> (italics). Such presentational code has been removed from the HTML 4.01 Strict and XHTML specifications in favor of CSS solutions. CSS provides a way to separate the HTML structure from the content's presentation. See separation of style and content.

The document type definition (DTD)

All HTML documents should start with a Document Type Definition (or DTD) declaration. For example:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

This defines a document that conformes to the Strict DTD of HTML 4.01, which is purely structural, leaving formatting to Cascading Style Sheets. Other DTDs, including Loose, Transitional, and Frameset, define different rules for the use of the language.

Version history of the standard

HTML 2.0 — (RFC 1866) approved as a proposed standard September 22, 1995,
HTML 3.2 — January 14, 1996,
HTML 4.0 — December 18, 1997,
HTML 4.01 (minor fixes) — December 24, 1999,
ISO/IEC 15445:2000 ("ISO HTML", based on HTML 4.01 Strict) — May 15, 2000.

There is no official HTML 1.0 specification because there were multiple informal HTML standards at the time. Work on a successor for HTML, then called 'HTML+', began in late 1993, designed originally to be "A superset of HTML … [which] allows a gradual rollover from the previous format [HTML]" (Dave Raggett, September 1993). The first formal specification was therefore given the version number 2.0 in order to distinguish it from these unofficial "standards". Work on HTML+ continued, but this never became a standard.

The HTML 3.0 standard was proposed by the newly formed W3C in March, 1995, and provided many new capabilities such as support for tables, text flow around figures and the display of complex math elements. Even though it was designed to be compatible with HTML 2.0, it was too complex at the time to be implemented, and when the draft expired in September 1995 it was not continued due to lack of browser support. HTML 3.1 was never officially proposed, and the next standard proposal was HTML 3.2, which had dropped the majority of the new features in HTML 3.0 and had instead adopted many browser-specific elements and attributes which had been created for the Netscape and Mosaic web browsers. Support for math as proposed by HTML 3.0 finally came with the different standard MathML.

HTML 4.0 likewise adopted many browser-specific elements and attributes, but at the same time began to try to 'clean up' the standard by marking some of them as 'deprecated'.

There will no longer be any new versions of HTML. However, HTML lives on in XHTML, which is based on XML.

External links

Wikibooks has a textbook about HTML.

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