From Fedora Project Wiki

This is a Fedora Core 6 specific page and is only retained as a historical reference. Firefox 2.0 is provided in Fedora 7.

For a variety of reasons , we are not planning to update to Firefox 2.0. We are instead focusing resources on Firefox 3.0, which will provide much more substantial benefits. We understand that some users will be willing to accept the risk of running Firefox 2.0 to gain compatibility with new extensions (e.g., Zotero and Halfnote). We have made available an experimental version of Firefox 2.0. However, we must stress that we believe the best experience for Fedora users will be to stay with Firefox 1.5 and wait for the Firefox 3.0 update. The experimental development version is available here:

Alternatively, it might make more sense to point users to the parallel install package submitted for review for inclusion in Fedora Extras and now been closed as per discussions with the Firefox maintainer and others. .

Having Firefox 2.0 coexist with Firefox 1.5 would make it easier for users to safely evaluate whether FF2.0 is ready to meet their needs (e.g., is compatible with their favorite extensions).

See also this bug that tracks the general issue of best recommendation to give users wishing to install Firefox 2.0 on Fedora Core 6.:

Better Collaboration

ChristopherAillon is working to improve the Firefox experience on Linux distributions. Refer to the following blogs for more details