Install or Upgrade Latest version of Mozilla Firefox On Ubuntu

Download latest stable version of firefox.
click here

If there is a directory name 'firefox' in /usr/lib, Rename it to old.
$ mv /usr/lib/firefox /usr/lib/firefox_old

 Extract your downloaded compress file and put it in /usr/lib
$ tar -xvf  firefox-new-version.tar.gz
$ mv  firefox-new-version /usr/lib

Now open it and make a link of filename 'firefox'.

   To make link, right click on the file and click 'Make Link'

 Now put this link file into /usr/bin and make sure it's name is 'firefox'.
$ sudo ln -s /usr/lib/firefox-new-version/firefox /usr/bin

 Now open firefox, it will open the latest version.

 Now you don't have to upgrade every time for latest version.

   Once you put the latest version , firefox is upgraded automatically, if it gets internet connection.

 If you want to know that your version is updated or not.

   In firefox menu, click on Help -> About firefox.

   If your version is not updated, it starts upgrading.

But above step does not help you in upgrading, if your version is too much old.

   Example: you are using 6 or 7 and current version is 15.

Enjoy firefox on Ubuntu