Just noticed this. The latest Firefox 3 Beta ( at present Beta 3 RC ) is now available in the Ubuntu Gutsy Repositories. The Ubuntu guys had not updated the Firefox 3 Alpha in the repositories for a long time, but now it is done.
To install the latest Firefox 3 Beta in Ubuntu Gutsy
- Go to System —> Administration —> Software Sources
- Then go to Updates tab, and tick “Unsupported Updates” checkbox.
- Click Close. Ubuntu will ask you to reload the software list. Click Reload.
- Then open a Terminal window and type apt-get install firefox-3.0
After installing, goto Applications —> Internet —> Firefox 3 Web Browser.
The Firefox 3 Beta will not replace your existing stable install of Firefox 2. So don’t worry. 
All your Firefox 2 settings and add-ons will remain intact. 
Akhil Bansal
12 Feb 08 at 3:57 pm
Hi,
I just installed it and it is working fine.
Thanks for the TIP
Manas
12 Feb 08 at 4:07 pm
@ Akhil – Glad to have helped you…
EoRaptor013
29 Feb 08 at 8:58 am
As of today (2008-02-28) the Ubuntu repository still holds Firefox 3.0-beta3pre, not the final beta 3 release.
Manas
2 Mar 08 at 10:55 am
You are right. Sad that the Ubuntu developers are not updating the repository.
Andrew
2 Mar 08 at 11:13 am
Mozilla Firefox will work in WinXP?
Or only in Ubuntu?
Manas
2 Mar 08 at 1:09 pm
Mozilla Firefox works on all platforms Windows, Linux and OS X.
Jebus
25 Apr 08 at 9:08 pm
“Mozilla Firefox will work in WinXP”
Are you stupid, or blind? Cuz those are the only 2 answers to your questions.
Mikko Ohtamaa
18 Jun 08 at 2:07 pm
Looks like backports still contains beta4. Can’t wait for the release version!