If you have just upgraded to Firefox 3.5 and have noticed the blurry fonts, and, or Firefox hangs if you put flash video on full-screen, I’ve got 2 workarounds for you.
Blurry font fix
su cd /etc/fonts/conf.d ln -s ../conf.avail/10-hinting-full.conf . rm 10-hinting-slight.conf 10-hinting-medium.conf
Then restart Firefox – you should see the font changes.
Please note I am using full hinting – change the above to your hinting level as per your configuration.
I found the above solution from this page.
Flash video full-screen hang fix – This also applies to Firefox 3.0 as well!
Insert the following line to the Firefox startup script (/usr/bin/firefox):
I got this fix from this page.