I apologize for any disrespect, but "FireFox" is a graphical web browser typically used by people that already have an existing X environment setup on their Unix-based desktops.
Now that you've "updated" this system to version 7.2 of FreeBSD, presuming it's local.. setting up X is typically quite simple these days, but you will probably want to decide on a windowing environment for X.
If you can post a dmesg here in [code][/code], we can attempt to help you with platform specific things..
This might be of some assistances:
http://www.freebsd.org/doc/en/books/handbook/x11.html
Good luck.. we look forward to some future replies.