Mozilla dropped me an email last night noting that the latest Firefox 3 beta milestone has been achieved:

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.

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.