HOWTOThe long awaited Firefox 4.0 was just released. Ubuntu Mozilla Team
has conveniently packaged it for Ubuntu 10.04 and 10.10. The packages
are available in their stable Personal Package Archive (PPA). In order
to get Firefox 4.0 for your 10.04 or 10.10 installation follow these
simple steps: - Add the Mozilla Team PPA to the list of your repositories:
sudo add-apt-repository ppa:mozillateam/firefox-stable && sudo apt-get update
- Run Update Manager and hit Install Updates.
Close all instances of Firefox. Next time you launch Firefox you will be greeted by 4.0. Optionally go to: http://www.webkit.org/perf/sunspider-0.9.1/sunspider-0.9.1/driver.html and enjoy the fireworks! Flash Flickering and Artifacts on 64bit Ubuntu
In case you are experiencing flickering and/or artifacts in Flash on 64bit Ubuntu you may want to look at this HOWTO. | 
