Firefox 5 beta ppa is available for Ubuntu user. The ppa is available in Mozilla firefox beta channel. The new certain improvement including support for css animation standard and channel switcher can be seen in Firefox 5. The new installation will upgrade your current firefox version to 5. Please note that firefox 5 is still in beta therefore the bugs are likely to been seen.
To install Firefox 5 Beta Open terminal (ctrl +alt+t) and run the following command
sudo add-apt-repository ppa:mozillateam/firefox-next sudo apt-get update sudo apt-get upgrade sudo apt-get install firefox