Firefox Fonts too small

The small and difficult to read fonts in Firefox 3: here is how to fix this:

1. Go to about:config in Firefox. To do so type about:config in the address bar.
2. Navigate to layout.css.dpi by typing layout in the filter bar.
3. Double click it and set to 0. By default it is -1
4. Restart Firefox.
5. Done.

Now all the options under Edit > Preferences > Fonts & Colors should work as expected.