Mozilla unleashes sleek new Firefox Web browser

A fast, sleek new version of Firefox was released on Wednesday to vie Microsoft's Internet Explorer 9 (IE9) and Google Chrome in the fiercely competitive market for Web browsing software.

Nonprofit group Mozilla made Firefox 4 available as a free download to computers powered by Windows, Mac OS X or Linux operating systems in more than 80 languages.

Firefox 4 was billed as six times faster than its predecessor and boasted features including a "Do Not Track" signal to opt-out of having online activities recorded by websites for targeted online ads or services.

The open-source Web browsing software was also designed as a stage for rich video or game graphics based on the HTML5 standard being touted as a boon for online visual experiences.

"Firefox puts users in control of their Web experience, providing a streamlined user interface, fun new features, a boost in speed and support for modern Web technologies," Mozilla said in an online message.

Powerful new versions of Chrome and IE9 Web browsers were released earlier this month by Google and Microsoft, respectively, putting pressure on California based Mozilla to release a finished version of Firefox 4.

Microsoft's Internet Explorer is the most widely used Web browser in the United States followed by Firefox, Chrome and Apple's Safari.