is the number of FreeBSD technologies integrated into the browser. The most widely publicized is probably the addition of Jason Evan's memory allocator (jemalloc) written for FreeBSD 7.0 which has been included into Firefox to reduce memory fragmentation. A nice blog post by one of the Firefox developers explains the benefit of jemalloc to Firefox.

Another FreeBSD technology widely adopted by other products utilizing binary updates is Colin Percival's bspatch client-side binary patching code. Kris Kennaway also notes that the ISC is hosting its FireFox mirrors on FreeBSD 7.0 machines to handle the unprecedented download demand as the Mozilla Foundation attempts to break a world record for downloads in a day.