HTML5: An introduction

Author: abhi2810 on Aug 14, 2010
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HTML5 is currently under development as the next major revision of the HTML standard. Like its immediate predecessors, HTML 4.01 and XHTML 1.1, HTML5 is a standard for structuring and presenting content on the World Wide Web. The new standard incorporates features like video playback and drag-and-drop that have been previously dependent on third-party browser plug-ins such as Adobe Flash, Microsoft Silverlight, and Google Gears.

HTML5 introduces a number of new elements and attributes that reflect typical usage on modern websites. 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> (usually referring to bottom of web page or to last lines of html code). Other elements provide new functionality through a standardized interface, such as the multimedia elements <audio> and <video>.
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. There is also a renewed emphasis on the importance of DOM scripting (e.g., JavaScript) in Web behavior.
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, <!DOCTYPE html>, which enables standards-compliant rendering in all browsers that use "DOCTYPE sniffing".
HTML5 also incorporates Web Forms 2.0, another WHATWG specification.

New APIs

In addition to specifying markup, HTML5 specifies scripting application programming interfaces (APIs). Existing document object model (DOM) interfaces are extended and de facto features documented. There are also new APIs, such as:
  • The canvas element for immediate mode 2D drawing. See Canvas 2D API Specification 1.0 specification
  • Timed media playback
  • Offline storage database (offline web applications).
  • Document editing
  • Drag-and-drop
  • Cross-document messaging
  • Browser history management
  • MIME type and protocol handler registration.
  • Microdata
  • Geolocation
  • Local SQL Database. Web SQL Database
  • Indexed hierarchical key-value store (formerly WebSimpleDB). Indexed Database API
Some of the new features are part of HTML5 and some are maintained in separate specifications.




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