Alright guys, its time to upgrade your Firefox into the latest one(3.5), now I’m gonna provide some simple steps to install Firefox 3.5:
1. Don’t forget to backup your previous version of Firefox first by typing:
cp -r ~/.mozilla/firefox/ ~/firefox_backup
2. Put this following command inside your terminal:
wget -O – http://releases.mozilla.org/pub/mozilla.org/firefox/releases/3.5/linux-i686/en-US/firefox-3.5.tar.bz2 | tar xj -C ~
3.To open Firefox, go to your home folder -> open Firefox Folder -> Double Click the Firefox file. You also can open Firefox 3.5 by this command ~/firefox/firefox
4. To add Firefox application into the main menu, go to System -> Preferences -> Main Menu
5. In “Command Field” room, add you firefox directory, for example: /home/username/firefox/firefox
6. In the “Name Field” room , type Firefox 3.5
And now, you’re all set to go! Comments and inputs are greatly appreciated.

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[...] trying out the new Firefox for yourself before the powers that be get it ready for the repos, visit this page for an in depth way to accomplish it. It’s easy and it works like a [...]
Firefox 3.5 is in the ubuntu repositories. All you need to do is:
apt-get install firefox-3.5
This will also keep your firefox 3.0 installed.
I always like the firefox and its really nice to heard the news about the firfox is now update and its update version is available to install now.