Howtoforge posted a guide about installing Firefox 4.0 (.deb Package) on Ubuntu 10.10
In this short guide I will show you how you can install the new Mozilla Firefox 4.0 browser (released March 22, 2011) on an Ubuntu 10.10 desktop. Fortunately, there's a Launchpad PPA repository that has Firefox 4.0 .deb packages, so we can easily install it through Ubuntu's package manager.Installing Firefox 4.0 (.deb Package) On Ubuntu 10.10