I had problems with the fonts when I changed from Ubuntu to Gentoo. With gtk-theme i could fix the problem with most of my tools. However, the fonts for Firefox, Thunderbird and Seamonkey were still ugly. As none of the mozilla progammes having direct acces to these settings by the preference menu, I started to search for a solution. According to the suggestion to use a ~/.fonts.conf to change my settings, I went on to the userChrome.css file as I failed with the ~/.fonts.conf. This file is in every profile folder of mozilla tools in the folder /chrome, if not, you have to create it. This file regulates the settings for the design in menu and fonts. I used a global setting, because I wanted to have the settings for fonts in every part of my mozilla tools. The guys who want to config it more in detail should take a look to the following sites:

Userstyles
Customizing Mozilla

My userChrome.css looks now like this:

* {
font-family: fixed !important;
font-size: 10px !important;
}

The font depends now on my setting in gtk. Here it is “Terminus”, but you are free to use your own favorite. The font-size should be small and equal but still readable, so I took 10px. The “px” is important, otherwise there will be some parts in the menu that would not be affected by the config.

Here are some screenshots of my config in Firefox, Seamonkey and Thunderbird:

FirefoxSeamonkeyThunderbird