HTML 5 is a new version of HTML 4.01 and XHTML 1.0 focusing on the needs of Web application developers as well as evolving HTML and addressing issues found in the current specifications.
Why Should You Learn HTML 5
HTML 5 is the newest specification for HTML, and many browsers are going to start supporting it in the future. One nice thing about HTML 5 is that it attempts to stay backwards compatible. So if you don’t want to learn it just yet, you don’t need to.
If you build Web applications you will eventually want to learn HTML 5. There are a lot of new attributes and tags built just for Web applications. For instance, there are a number of new event handlers for drag and drop: