Overview

HTML5 is being developed as the next major revision of HTML (HyperText Markup Language), the core markup language of the World Wide Web. According to the W3C timetable, it is estimated that HTML5 will reach W3C Recommendation by late 2010.

HTML5 is the proposed next standard for HTML 4.01, XHTML 1.0 and DOM Level 2 HTML. It aims to reduce the need for proprietary plug-in-based rich internet application (RIA) technologies such as Adobe Flash, Microsoft Silverlight, Apache Pivot, and Sun JavaFX.

The HTML5 syntax is no longer based on SGML despite the similarity of its markup. It has, however, been designed to be backward compatible with common parsing of older versions of HTML. It comes with a new introductory line that looks like an SGML document type declaration, , which enables standards-compliant rendering in all browsers that use "DOCTYPE sniffing"...

Markup

HTML5 introduces a number of new elements and attributes that reflect typical usage on modern Web sites. Some of them are semantic replacements for common uses of generic block (<div>) and inline (<span>) elements, for example <nav> (website navigation block) and <footer>. Other elements provide new functionality through a standardized interface, such as the <audio> and <video> elements.

Some deprecated elements from HTML 4.01 have been dropped, including purely presentational elements such as <font> and <center>, whose effects are achieved using Cascading Style Sheets...

The most eagerly anticipated additions to HTML5 are the new elements and APIs that enable content authors to create rich media using nothing more than standards-based HTML. Modern Web pages increasingly incorporate scalable graphics, animation, and multimedia, but so far these capabilities have required proprietary plug-ins such as Flash, RealMedia, and QuickTime. Such plug-ins not only introduce new security risks, but they also narrow the audiences of the resulting pages.

Web developers are clamoring loudest for HTML5's new audio and video tags, which aim to finally make it easy to embed multimedia content into Web pages...