As it turns out, I'm posting this on Firefox 4 via RHEL 5.4. It is possible, and I would highly recommend visiting http://forums.mozillazine.org/viewtopic.php?f=23&t=2075033 for instructions on getting it running. I can try and help if people have specific issues, but this worked for me.

Sigh, even the site you point to has an extensive discussion on why Firefox should have support for enterprise systems. We can't expect (nor, for that matter, allow) all users to go through the steps to hack their systems so that they can use Firefox. After all Firefox 4 is supported on XP and it's older than CentOS 5. What is the message that Mozilla is sending to world?

Oh, and when you follow the instructions in http://forums.mozillazine.org/viewtopic.php?f=23&t=2075033 you still get:

./firefox-bin: /usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.9' not found (required by /usr/lib/firefox/libxul.so)

So even if we gave this to our users they would still be unable to use it.

See also /questions/777306

Posing a link to a page that rehashes the same non-solution as the one already posted here is not very helpful.

Let's just be honest and admit that Firefox 4.0 is only really meant for enterprise Windows users. Individuals who use Linux at home are probably thrilled with it as well. But for the enterprise Linux users, stay on 3.6 -- hopefully they will patch any critical security issues that arise..

Again, I have Firefox working on RHEL 5.4 (full Flash support and everything). The above mozillazine forum post fixed it up for me, what problems are you having? I'm not giving up (on love)...

See my message from 4 days ago. Even after following the instructions I still get the ./firefox-bin: /usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.9' not found (required by /usr/lib/firefox/libxul.so)

However this is a bigger issue than my not getting it to work. In an enterprise situation it is not a "simple" matter of copying some library and then it all works. The tools have to be qualified and security needs to be maintained. Even if most enterprise users understood the instructions the IT group gets very nervous when it has to copy a non-standard library. Trying to sell that to the group is rather hard. The decision to abandon CentOS 5 for firefox 4 was most unfortunate, especially as it was working for most of the beta test period.