As we all know Mozilla is currently working on the upcoming version 4.0 of its web browser Firefox and continuously releasing Alpha builds for testing purposes:
Mozilla Puts “Aero Glass” Back in the Latest Firefox 3.7 Alpha 5 Preview Build
Its still named as Firefox 3.7 but later it'll be changed to 4.0.
Now a good news for 64-bit users. Mozilla has started releasing official builds for 64-bit hardware architecture. Currently an Alpha build is available for download and testing:
Download Mozilla Firefox 4.0 64-bit (x64) Version
Please note that its a testing build and should not be used as primary browser. Also it only uses 64-bit versions of plug-ins so most of your favorite plug-ins will not work like Flash Player, etc. Although an Alpha version of Flash Player is available for Linux users.
PS: If you get a missing MSVCR100.dll file error while running Firefox 64-bit version, download and install
Microsoft VC++ Redistributable Package.