The fourth beta release of Firefox 3 is available for download today from Mozilla.

Grab it here (http://www.mozilla.com/en-US/firefox/all-beta.html) if you're feeling adventurous. Remember it's a beta, so beware of rushing to code where angels fear to thread.

The browser's latest build boasts several improvements over previous beta releases, including a speed boost, full-page zoom, a revamped download manager, tighter OS integration, and the plugging of Firefox's rather irksome memory leaks.

Perhaps the most noticeable advancement user-side is performance. Tweaks to the Beta 4 JavaScript engine will double the speed of script-heavy web applications like Google Mail and Zoho Office, compared to Firefox 2, so say some release notes.

Memory leak issues — a major thorn in Firefox's paw since 1.0 - continue to be addressed by the Mozilla's open-source team.

"Several new technologies work together to reduce the amount of memory used by Firefox 3 Beta 4 over a web browsing session. Memory cycles are broken and collected by an automated cycle collector, a new memory allocator reduces fragmentation, hundreds of leaks have been fixed, and caching strategies have been tuned," we're told.

As for cosmetics, Beta 4 has an improved native user interface for XP, Vista, OS X and Linux. This includes work on the browser's menus, icons and various controls to match the operating systems.

Mozilla said its souped up download manager makes it easier to locate downloaded files, and now lets a user search a website for where a file came from. A new zooming feature can scale the entire layout, text and images of a website, as opposed to only the text size in previous incarnations.

All-in-all, Mozilla said its made over 900 improvements to Firefox from Beta 3. Mozilla's Percy Cabello has an in-depth summary of the various changes including screen shots here (http://mozillalinks.org/wp/2008/03/firefox-3-beta-4-review/). Release notes are over yonder (http://www.mozilla.com/en-US/firefox/3.0b4/releasenotes/).

So when is version 3 going public? Well, there's at least one more beta to go. The development team confirmed the code will be frozen March 18 for a fifth preview of the build. ®

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