HTML5 is not yet an official standard, and no browsers have full HTML5 support. But all major browsers (Safari, Chrome, Firefox, Opera, Internet Explorer) continue to add new HTML5 features to their latest versions.
HTML5 Introduction
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>.
Greater Consistency
As websites adopt the new HTML5 elements we will see far greater consistency in terms of the HTML used to code a web page on one site compared to another. This will make it far easier for web designers and web developers to immediately grasp how a web page is structured even if they are brand new to it.