How to fix font rendering of Firefox 3.5 under Ubuntu 9.04

The problem is that Firefox 3.5 doesn't seem to use font hinting and therefore looks ugly while the default version (3.0) is OK.

After some googling I found out that 3.5 doesn't use GNOME font settings and relies on fontconfig.

Font configuration is stored in /etc/fonts/conf.d/[0-9][0-9]*.conf files. By convention, config files starting with 10 through 19 control font rendering (see /etc/fonts/conf.d/README) and, in fact, are symlinks to the corresponding files in the /etc/fonts/conf.avail directory.

My experiments have shown that it is enough to disable the 10-hinting-slight.conf symlink by removing or just renaming it:

  sudo mv /etc/fonts/conf.d/10-hinting-slight.conf{,.disabled}
  sudo dpkg-reconfigure fontconfig

Source: http://www.timka.org/tech/2009/05/02/firefox-3.5-in-jaunty/