If you got the firefox installer from mozilla.org, you really didn't have to. The simplist way to get the latest Firefox version is to either use up2date or use yum. I prefer yum. If you haven't done so already, get the yum.conf at http://www.fedorafaq.org/#getsoftware
and do (as root):
Or if you want to update your entire system do:
This may take a while depending on how many packages need updating.
If you already downloaded the firefox rpm from an update mirror you can just do this as root:
rpm -Uhv firefox_rpm_name.rpm
Hope this helps