Mozilla releases Firefox 4 Beta 9..

The Mozilla Project has published the ninth beta for version 4.0 of its open source Firefox web browser. Firefox 4 is the non-profit organisation's next-generation web browser based on version 2.0 of the Gecko rendering platform (the Firefox 3.6 branch uses Gecko 1.9.2) and features a new Add-ons Manager and extension management API. Other changes include a new 'tabs on top' layout, the integration of Firefox Sync, formerly known as Weave, and various new features aimed at web developers.

Firefox 4 Beta 9 on Mac OS X. According to a post on the Mozilla Blog, compared to the previous beta, Firefox 4 Beta 9 focuses on performance and features improvements to the browser's start-up time, as well as an overhaul of the bookmarks and history code. The developers have also enabled per-compartment garbage collection, reducing the amount of work that needs to be done during complex animations and making them smoother. Other changes include the addition of a new database standard, IndexedDB, which replaces Web SQL and fixes for more than 650 bugs.
As with all development releases, use in production environments and on mission critical systems is not advised. Users testing the release are encouraged to provide feedback and report any bugs that they encounter. The ninth beta will be followed by one more beta version, as well as the planned release candidate – specific release dates for these have yet to be confirmed. Following a number of delays, the final release of Firefox 4 is expected "before the end of February".
Further information about the development preview, including a list of known issues, can be found in the release notes and in the change log. Firefox 4 Beta 9 is available to download for Windows, Mac OS X and Linux. Alternatively, existing Firefox 4.0 Beta users can upgrade to the new version, either by waiting for the automated update notification or by manually selecting "Check for updates" from the Help Menu.
Firefox binaries are released under the Mozilla Firefox End-User Software License Agreement and the source code is released under disjunctive tri-licensing that includes the Mozilla Public Licence, GPLv2 and LGPLv2.1. The latest stable release is version 3.6.13, a security update that addressed a critical vulnerability, from early December.