To make Firefox match your Gnome font rendering setting, simply erase the following file links in the /etc/fonts/conf.d folder
10-antialias.conf
10-hinting.conf
10-hinting-slight.conf
In a terminal type,
cd /etc/fonts/conf.dsudo rm 10-*.conf
Restart Firefox for the changes to take effect.
How to restore the symbolic links
sudo ln -s /etc/fonts/conf.avail/10-antialias.conf /etc/fonts/conf.d/
sudo ln -s /etc/fonts/conf.avail/10-hinting.conf /etc/fonts/conf.d/
sudo ln -s /etc/fonts/conf.avail/10-hinting-slight.conf /etc/fonts/conf.d/
