Mozilla's brand new web browser designed to compete head on with Microsoft's Internet Explorer 9 (IE9). The new Firefox will feature redesigned user interface, JaegerMonkey JavaScript engine, built-in sync feature, hardware acceleration and support for technologies like HTML5, CSS3 and WebGL.

Just like the newly released IE9, Firefox 4 will also come with "Do Not Track" feature to let users to notify ad companies and websites that they don't want their online history to be tracked. This functionality of IE9 and Firefox 4 could force to include similar features in its Web browser Chrome.