Changelog:
The final release of Firefox 4 is expected next month.Firefox 4 Beta 5 is available in 39 languages. Support for the new proposed Audio Data API Direct2D Hardware Acceleration is now on by default for Windows 7 users Firefox button has a new look for Windows Vista and Windows 7 users Support for HSTS security protocol allowing sites to insist that they only be loaded over SSL.
Source: Neowin