The Help > check for updates is either removed or greyed out in the third-party builds of Firefox. One cannot expect Mozilla to provide update patches to builds they did not well build. To be honest, fedora 8 (Nov 2007) is old enough that you may not have the packages or the versions of them needed at minimum in order to be able to run Firefox 4.0 and newer including 9.0.1. Unless you upgrade to a newer Fedora (or another distro that is not LTS) your best bet is to use Firefox 3.6.* which is still supported with security updates as 3.6.25 was released recently. https://www.mozilla.org/en-US/firefox/all-older.html