Mozzilla devolopers are now testing the next stable build of the Firefox 3.5.x series. Firefox 3.5.7 is now available as a beta build for TESTERS to try out. The 3.5.7 dev update milestone follows closely on the heels of the Firefox 3.5.6 update which came out December 2009.
Please note that installing Firefox 3.5 will overwrite your existing installation of Firefox. You won’t lose any of your bookmarks or browsing history, but some of your extensions and other add-ons might not work until updates for them are made available. You can reinstall an older version later if you wish to downgrade.