I really wanted to upgrade my Firefox in FC4. When I tried using yum it updated Firefox 1.0.4 to 1.0.7. I tried adding extra mirrors in yum configuration but no use.

Latter I found a manual method to update Firefox.

su or login as root first.
# wget ftp.mozilla.org/pub/mozilla.org/firefox/ .. /firefox-1.5.tar.gz
# cd /usr/lib
# tar xzvf ~/firefox-1.5.tar.gz
# mv firefox firefox-1.5
# which firefox
/usr/bin/firefox
# cd /usr/bin/
# mv firefox old.firefox
# ln -s /usr/lib/firefox-1.5/firefox

Thanks to Philip for sharing this. I followed the same instruction to update Firefox 1.5.1 and it worked.

su or login as root first.
# wget ftp.mozilla.org/pub/mozilla.org/firefox/.. /firefox-1.5.0.1.tar.gz
# cd /usr/lib
# tar xzvf ~/firefox-1.5.0.1.tar.gz
# mv firefox firefox-1.5.0.1
# which firefox
/usr/bin/firefox
# cd /usr/bin/
# mv firefox old.firefox
# ln -s /usr/lib/firefox-1.5.0.1/firefox

Cool… ;-)