Change Thunderbird CSS styles

Thunderbird profile folder can be found here: chrome folder

In Ubuntu 10.04 the chrome folder should be created in the profile folder which is located here: ~/.mozilla-thunderbird/profileName/ (/home/userName/.mozilla-thunderbird/profileName/)

Create chrome folder (named chrome) if it does not exists.

In this folder create the file userChrome.css if it does not exists (this file does not exist in a new profile).

Detailed instruction to customize the CSS file can be found on this page: Pane and menu fonts

For example, to change all the font in Mozilla Thunderbird to Arial  (or other sans serif font if Arial is not available) with a size of 11px add the following code to he CSS file:

* {
   font-family: arial, verdana, helvetica, sans-serif !important;
   font-size: 11px !important;