HTML5 has already made a lot of waves in the web developer community. Now, HTML5 has a lot more to offer than it had a year back! (You can read more about the newer features of HTML5). Although HTML5 is still under review and active development, it has not failed to make it to the Facebook Code Base. In this article we will tell you about 5 ways in which Facebook is currently using HTML5.

• Facebook's Video player on iPhone and the iPad is built with HTML5 video and supports hi-def H.264 video. However tests have indicated that Flash still outperformed HTML5 video implementations on the Facebook video platform

• Facebook Places that was unveiled recently makes use of the HTML5 Geolocation API which is available on the browsers for Android, iPhone, and any other mobile device with similarly modern browsers. You can access Facebook Places at http://touch.facebook.com/.

• You must be familiar with the strange way Facebook used to append URL locations in the address bar - something like this: “profile.php?id=1586010043#!/pages/Haskell/401573824771” (Note the hash and the exclamation mark). This method was used to store the current application state. However, you won't be able to see these ugly URLs any more as Facebook has implemented the History API of HTML5 to enable selective loading of page content via AJAX while preserving readable URLs.

• Facebook is currently experimenting with Web Storage to cache typeaheads, CSS and JavaScript for use in lower bandwidth environments such as mobile devices.

• You must have experienced kinks while using Facebook Chat. Experiments are now going on with HTML5 WebSockets that will make real-time web apps like Chat more stable.

via Facebook Notes