You might also want to download Firefox-4.0b8pre

And always check this page to find the latest updates for Firefox.

http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-trunk/

The precursory releases are currently codenamed “MineField" and it is not a final version of Firefox. And it is provided without any guarantees of stability and you should back up your profile regularly as there may be bugs that corrupt your data...
More info Here.
I tried Minefield b8pre, but was not satisfied with it at all. It felt very sluggish for a reason!
I prefer Betas over Nightly Builds.
6 days later
Xsever wroteI tried Minefield b8pre, but was not satisfied with it at all. It felt very sluggish for a reason!
I prefer Betas over Nightly Builds.
I've been using minefield since the last update in this topic. and i found it pretty interesting. It's fast, reliable, with low memory consumption and outstanding performance.