How to update firefox

How To Install firefox-3.0.tar.bz2 in Linux

A. You won't lose any of your bookmarks or browsing history created by Firefox 2.0, but some of your extensions and other add-ons might not work until updates for them are made available.

Backup Existing Firefox 2.0 Settings

Just backup existing Firefox 2.0 settings:
$ mkdir ff.backup/
$ cp -avr .mozilla/ ff.backup/

Installing Firefox 3 on Linux

Just use the following instructions to download and install Firefox.

Download Firefox 3.0 for Linux

Visit official website to grab latest version. You can also use wget command to download firefox.
$ cd /tmp
$ wget 'http://download.mozilla.org/?product=firefox-3.0&os=linux&lang=en-US'

Linux Install Firefox for all users

First close all running old Firefox 2.x sessions. Login as the root and type the following command to move old firefox 2 and install Firefox 3 under Linux:
# cd /opt
# mv firefox firefox.old
# cp /tmp/firefox-3.0.tar.bz2 .
# tar -jxvf firefox-3.0.tar.bz2

To start firefox, enter:
$ /opt/firefox/firefox &

source:http://www.cyberciti.biz/faq/install-firefox3tarbz2-linux/