Programmer Armen Zambrano Gasparnian announced the first 64-bit Firefox builds for Windows on Friday, offering an FTP site for those who want to download it. But the software isn't for mainstream users yet.
For one thing, there's no installer included yet
Apple's Safari, however, already made the 64-bit jump with Mac OS X 10.6, released in 2009. Internet Explorer on 64-bit Windows is offered in 32-bit and 64-bit versions. Google is working on 64-bit Chrome, too, though it appears the Windows version is a lower priority than 64-bit Mac OS X and Linux versions.
UserAgent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.1.9) Gecko/20100315 Firefox/3.5.9






I'm going to ask over at the Ubuntu forums.