What parts of HTML5 can we use today?

Although the full specification of HTML5 is yet to be ratified, most new features of HTML5 are already supported, to varying degrees, by modern web browsers including Apple's Safari, Google Chrome, Opera, and Mozilla Firefox and even Internet Explorer 9! So, whilst it's improbable everything in the current draft of the HTML5 specification will survive until recommendation by the W3C, there are plenty of new features that can be implemented right now.

Most sites can be written in HTML5

Currently, if I'm tasked to build a website, my default markup would be HTML5 rather than HTML 4.01. Where the opposite was the case only a few years ago, at present, there has to be a compelling reason not to markup a site in HTML5. All modern browsers understand common HTML5 features with no problems (the new structural elements, video and audio tags) and older versions of IE can be served polyfills to address all of the shortfalls I have encountered.

Note

What are polyfills...