Mozilla has released a major revamp to Firefox, doubling the browser's speed and introducing private browsing, location-aware browsing and HTML 5-based open video support.

Firefox 3.5, made available for download last week, is the first major update to the browser since version 3, which was released a year ago. The new version began life as Firefox 3.1, but Mozilla decided the number of enhancements involved in the new version made it a more important upgrade than was first planned.

A new TraceMonkey JavaScript engine has been added to Firefox 3.5, making the browser more than twice as fast as Firefox 3, and 10 times faster than Firefox 2, Mozilla said last week.

Other browsers, such as Chrome and Internet Explorer 8, already include private browsing, but Firefox 3.5 is the first edition of Mozilla's browser to do so. Private browsing allows the user to leave no easily findable trace of a browsing session, although such traces can still be found through the ISP's logs.

Two aspects of private browsing in Firefox 3.5 are unique, according to Mozilla. These are the 'Forget this Site' feature, which removes all trace of a particular site from the browser's history, and the 'Clear Recent History' feature, which removes traces of the last few hours' browsing.

Location-aware browsing is also particular to Firefox 3.5. Certain websites, such as a site that helps you search for the nearest restaurant, can provide information that relates to the user's location. In addition, the updated Firefox will ask visitors to such sites whether they want to share their geographical data with the site.