This quick guide is made for home user who are not familiar with official installation of firefox5.
Open terminal and run the following commands
sudo add-apt-repository ppa:mozillateam/firefox-stable
This will install the repository of firefox5
sudo apt-get update
This will update your package manager with the new firefox5
sudo apt-get install firefox
Tadaaaa….. now close your firefox and open it.
To check the version of firefox click on “help” menu and click the “about firefox”