HTML5 is like just other html i.e., .html we generally use for our web pages.HTML5 is currently being developed as the next major revision of HTML (HyperText Markup Language), the core markup language of the World Wide Web.
So you might be thinking what the big deal in the html5 and why steve jobs i mean apple is supporting it ???
Because, It aims to reduce the need for proprietary plug-in-based rich internet application (RIA) technologies such as Adobe Flash and Microsoft Silverlight.
