If Firefox 4 is compatible with old versions of Windows (going all the way back to Windows 2000) Why is it not compatible with at least Mac OS X 10.4!? I bought my Mac in 2006 with the latest version of OS X. How is this fair?
The newest version of Firefox (Firefox 4) is not compatible with anything before Mac OS X 10.5 which was released in 2007. If you support Windows 2000 then you should definitely support OS X 10.4 just based on release date alone. Also after finding out my operating system is incompatible after downloading Firefox 4, the number other people having the same problem should indicate that there is plenty of reason to continue to develop a browser that is compatible with OS X 10.4.
Opaite Mbohovái (1)
Because OS X 10.4* does not have what is needed by Firefox 4.0 and newer.
Linux users are in a similar boat also as they need certain package versions within the last few years as LTS distros (with outdated packages from 4+ years ago) like CentOS is a bit screwed on newer applications like Firefox 4.0. By your logic Mozilla should also support Linux packages from 10 years ago also which would be a really ridiculous thing to do.
I think only the 64-bit Windows Vista and Windows 7 is really supported or will be rather when it comes to 64-bit builds (still not officially supported yet).
Mozilla is still supporting Firefox 3.6 with updates, in which 3.6.16 can be found at http://www.mozilla.com/en-US/firefox/all-older.html