HTML 5 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 HTML 5 are functions for embedding audio, video, graphics, client-side data storage, and interactive documents. HTML 5 also contains new elements like <nav>, <header>, <footer>, and <figure>.
The HTML 5 working group includes AOL, Apple, Google, IBM, Microsoft, Mozilla, Nokia, Opera, and many hundred other vendors.
Note: HTML 5 is not a W3C recommendation yet!
Read more about HTML 5.0 tags
The new standard attributes in HTML 5 are: contenteditable, contextmenu, draggable, irrelevant, ref, registrationmark, and template.
The HTML 4.01 attribute which is no longer supported: accesskey.
Read more about HTML 5.0 Attributes
The new event attributes in HTML 5 are: onabort, onbeforeunload, oncontextmenu, ondrag, ondragend, ondragenter, ondragleave, ondragover, ondragstart, ondrop, onerror, onmessage, onmousewheel, onresize, onscroll, and onunload.
The HTML 4.01 event attribute which is no longer supported: onreset.
Read more about HTML 5.0 Events