Here is an instruction how to install these packageshttps://help.ubuntu.com/community/CompilingEasyHowTo

You should have read my complaint more closely. The info you gave DOES NOT do what I want, I need to revert not install a new program. I ended up deleting 4.0 and extracting the tarball to a directory, however I cannot get it to respond when I click on a link in another program such as Thunderbird or evince. I have placed FF in several different directories and even changed the path but no joy on anything I've done. I don't want to have to compile something, I just wanted to backdate to an earlier version. I read what you suggested but I have no idea what it means, nor do I want to find out what it means. I installed Ubuntu to use not to play with esoteric procedures such as you suggest. Right now I can run FF, just can't click on a link and have it call FF. Why isn't there a .deb file I can just put in to package manager? Seems as though there had to be one originally, where did it go and why can't I just find it on Mozilla.com and install it from there. It isn't as though one never existed!

Sorry if I misunderstood you. If you use Ubuntu, then you might try to install firefox with the help of Synaptic Package Manager.

The version which I have when I search for firefox in Synaptic is 3.6.18, I think it depends on the repository that one is using.

Chameau; I appreciate the reply, but neither synaptic nor package manager on 10.10 shows 3.6.18, they both show 4.0.1. I know there is a way to backtrack on an install but I can't find how to do it. This is one place windows has the advantage over Linux. Another is that in Windows you can tell the program what directory to use for the install. If Linux has either, I haven't found it. I'm about ready to use the live disk and see if I can get FF 3.6.x off it, but I don't know how to do that either. I don't want to wipe out my entire Ubuntu to do this but it is bad. I can't watch videos or play many games. MY grandson drove me crazy today because he wanted to play Lego Games and they require flash. I have flash but for some reason FF doesn't recognize it.

I see now, I use 10.04 and so I have different version of Firefox.

But, I have found one simple instruction to downgrade packages in Ubuntu.

May be you could try it: DowngradeInstruction

Here is another, more complicated instruction for downgrading, you might want to try it as well (if the previous one fails to help you).

Also, try directly downloading Firefox 3.6.18 package for Ubuntu 10.10 (maverick) from here . Then you should install it with Debian packages installer (gdebi-gtk). Of course, another versions of Firefox (if any) should be previously unistalled.

Complete list of packages for your Ubuntu version can be found here .

And btw, did you upgrade Firefox along with upgrading Ubuntu, or just Firefox?