If you use Ubuntu 10.04 or any other Linux distribution which doesn’t automatically upgrade your Firefox to the latest version you can force it.

First of all you have to launch Terminal and add the right PPA to the repository:

sudo add-apt-repository ppa:ubuntu-mozilla-security/ppa

Then you need to update and upgrade the OS using:

sudo apt-get update
sudo apt-get upgrade

If you are installing Firefox for the first time the right commands are:

sudo add-apt-repository ppa:ubuntu-mozilla-security/ppa

sudo apt-get updatesudo apt-get install firefox firefox-gnome-support
 firefox-locale-en

As usual on Linux, it is not necessary to reboot the computer and you can start immediately to use your updated Firefox.