HTML5 offers new features (elements, attributes, event handlers, and APIs) for easier web application development and more sophisticated form handling.
The HTML5 specification is based on HTML 4.01 Strict, but unlike previous HTML Recommendations, HTML5 does not use a Document Type Definition (DTD). Instead, it uses the Document Object Model (DOM, the “tree” formed by a document’s structure) as its basis rather than a particular set of syntax rules. It also differs from previous recommendations in that it includes detailed instructions for how browsers should handle malformed and legacy markup.
W3C and WHATWG
There are two organizations maintaining slightly different HTML specifications as of this writing.
HTML5 was originally written by the Web Hypertext Application Technology Working Group (WHATWG). In 2003, members of Apple, Mozilla, and Opera formed the WHATWG to further the development of HTML in a way that was consistent with real-world authoring practices and browser behavior. Their initial documents, Web Applications 1.0 and Web Forms 1.0, were rolled together into HTML5, which is still in development under the guidance of WHATWG editor, Ian Hickson. They eventually dropped the version number and now maintain “living” (unnumbered) HTML specification at whatwg.org.
In 2006, the World Wide Web Consortium (W3C) formed its own HTML5 Working Group based on the work by the WHATWG. In 2009, it discontinued its work on XHTML 2.0 in order to focus on the development of ...