The DevNews announcement has all details, and I'll copy/paste it here for those of my readers that won't click on the link. For those who want to know what's cool and exciting with this first Beta, please read the What's New? section of the release notes.

Please note: We do not recommend that anyone other than developers and testers download the Firefox 3 Beta 1 milestone release. It is intended for testing purposes only.

Firefox 3 Beta 1 is now available for download. This is the ninth 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 and on in #granparadiso.

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

  • Improved security features such as: better presentation of website identity and security, malware protection, stricter SSL error pages, anti-virus integration in the download manager, and version checking for insecure plugins.
  • Improved ease of use through: better password management, easier add-on installation, new download manager with resumable downloading, full page zoom, animated tab strip, and better integration with Windows Vista and Mac OS X.
  • Richer personalization through: one-click bookmarking, smart search bookmark folders, direct typing in location bar searches your history and bookmarks for URLs and page titles, ability to register web applications as protocol handlers, and better customization of download actions for file types.
  • Improved platform features such as: new graphics and font rendering architecture, major changes to the HTML rendering engine to provide better CSS, float-, and table layout support, native web page form controls, colour profile management, and offline application support.
  • Performance improvements such as: better data reliability for user profiles, architectural improvements to speed up page rendering, over 300 memory leak fixes, and a new XPCOM cycle collector to reduce entire classes of leaks.

(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 1 builds for Windows, Mac OS X and Linux in over 20 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 1 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.