HTML5 is the most exciting step forward in web development since the launch of XHTML 1.0 in the year 2000.HTML5 is the future of web design, but it can be implemented right now; and yet it does not make any of your current knowledge of HTML4 or CSS2 redundant. It is a welcome enhancement that increases the flexibility and usefulness of HTML. It also solves some problems; for instance, it can dispense with plugins for embedded video and audio clips, and the number of video file formats is drastically reduced. A raft of new semantic tags makes coding and maintaining a web site much easier. The number of DOCTYPES is reduced from six to two, and the HTML5 DOCTYPES are so brief that you can easily commit them to memory.
HTML5 offers new features (elements, attributes, event handlers, and APIs) for easier web application development and more sophisticated form handling.
New Semantic Elements in HTML5 :
HTML5 includes new semantic elements for marking up page content.
HTML5 introduces many APIs (Application Programming Interfaces) for the creation of web applications. APIs standardize tasks that traditionally required proprietary plug-ins or custom programming.