Mozilla launched Firefox 4 yesterday, the latest version of its free and open-source Web browser. It was released just a few days after Microsoft made the Internet Explorer 9 (IE9) available for download.

It supports Windows, Mac OS X or Linux operating systems in more than 80 languages. The browser boasts a number of improvements over past iterations, including a new look and feel, and increased privacy and security features.

A new feature called “Do Not Track,” will allow “users to set a browser preference that will broadcast their desire to opt-out of third party, advertising-based tracking,” according to Mozilla.

The new Firefox also promotes interactive capabilities with HTML5, which is now becoming a standard in modern web browsers.

Download English version (US) Firefox 4.0 for Windows or Mac. Other supported languages can be downloaded from Mozilla’s website.