HTML 5

HTML 5, the next major revision of HTML is proposed to be the next standard for HTML and XHTML
Some of the main differences that will exist between HTML 4 and HTML 5 include the following:

- new parsing rules
- new elements
- new attributes
- global attributes
- new form control types
- will not be based on SGML
- frames made invalid
- depreciated elements dropped

What the new HTML would mean for developers includes:

- the ability to create more user-friendly applications
- works well with JavaScript
- building browser-specific apps
- use with mobile devices
- wealth of APIs

Resources:
http://en.wikipedia.org/wiki/HTML_5#Differences_from_HTML_4.2FXHTML_1.x
http://www.smashingmagazine.com/2009/07/16/html5-and-the-future-of-the-web/