Firefox 3.5 or 3.6 Ubuntu Repository (deb)

To install the latest Firefox 3.5 (final) or Firefox 3.6 in Ubuntu, open a terminal and type:

sudo sh -c “echo ‘deb http://ppa.launchpad.net/ubuntu-mozilla-daily/ppa/ubuntu jaunty main’ >> /etc/apt/sources.list”

sudo sh -c "echo 'deb-src http://ppa.launchpad.net/ubuntu-mozilla-daily/ppa/ubuntu jaunty main' >> /etc/apt/sources.list"

Then add the Launchpad PPA GPG key:


sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 247510BE

And finally, install Firefox 3.5 or 3.6


sudo apt-get update && sudo apt-get install firefox-3.5

or

sudo apt-get update && sudo apt-get install firefox-3.6

If you already have a version of Firefox 3.5 installed from a repo then upgrade it:


sudo apt-get update && sudo apt-get upgrade

courtesy: http://webupd8.blogspot.com/2009/06/firefox-35-rc-1-ubuntu-repository-deb.html