Mozilla released the twelfth beta for Firefox 4.0 on February 25th. This is a regular beta release and is being made available for testing purposes only.

New stuff in this Beta 12 release:

• Increased performance while viewing Flash content
• Improved plugin compatibility with hardware acceleration enabled
• Hovering over links now displays the URL at the bottom of the window rather than in the location bar
• General stability, performance, and compatibility improvements
• See the complete changelist from the previous beta

For more info see the release notes for Firefox 4 Beta 12. The next planned release is the Release Candidate (RC) 1 (or Beta 13).