Web Definitions: HTML5 is currently under development as the next major revision of the HTML standard
HTML5 improves interoperability and reduces development costs by making precise rules on how to handle all HTML elements, and how to recover from errors.
Some of the new features in HTML5 are functions for embedding audio, video, graphics, client-side data storage, and interactive documents. HTML5 also contains new elements like <nav>, <header>, <footer>, and <figure>.
List of awesome sites developed in HTML5