[Mozilla announced Firefox 3 Beta 4 today, March 10th at approximately 5:30pm PT. See Mike ’s comprehensive post from DevNews, crossposted below. Please keep in mind that the Firefox 3 Beta 4 milestone release is intended for testing purposes only and is not for casual users.]

Please note: We do not recommend that anyone other than developers and testers download the Firefox 3 Beta 4 milestone release. It is intended for testing purposes only.

Firefox 3 Beta 4 is now available for download. This is the twelfth developer milestone focused on testing the core functionality provided by many new features and changes to the platform scheduled for Firefox 3. Ongoing planning for Firefox 3 can be followed at the Firefox 3 Planning Center, as well as in mozilla.dev.planning and on irc.mozilla.org in #granparadiso.

New features and changes in this milestone that require feedback include:

Improvements to the user interface: better search support in the Download Manager, ability to zoom entire page or just the text, continuing look and feel improvements on Windows Vista, Windows XP, Mac OS X and Linux.

Richer personalization through: location bar that uses an algorithm based on site visit recency and frequency (called “frecency”) to provide better matches against your history and bookmarks for URLs and page titles, as well as an adaptive learning algorithm which tunes itself to your browsing habits.

Improved platform features such as: support for HTML5’s window.postMessage and window.messageEvent, JavaScript 1.8 improvements, and offline data storage for web applications.

Performance improvements: changes to our JavaScript engine as well as profile guided optimization resulted in significant gains over previous releases in the popular SunSpider test from Apple, web applications like Google Mail and Zoho Office run much faster, and continued improvements to memory usage drastically reduce the amount of memory consumed over long web browsing sessions.

(You can find out more about all of these features in the “What’s New” section of the release notes.)

Testers can download Firefox 3 Beta 4 builds for Windows, Mac OS X and Linux in over 35 different languages. Please be sure to read the full release notes before using this preview release. Developers should look at the Firefox 3 for Developers article on the Mozilla Developer Center.

Note: Please do not link directly to the download site. Instead we strongly encourage you to link to this Firefox 3 Beta 4 milestone announcement so that everyone will know what this milestone is, what they should expect, and who should be downloading to participate in testing at this stage of development.