Another way to hack your configuration files is to edit them using a text editor. For both Firefox and Thunderbird, files can be edited, all of which need to be created first in the appropriate profile folder:
user.js userChrome.css userContent.css
To create these files, you need to locate your Thunderbird or Firefox Profile Folder. Tables E-1 and E-2 show profile locations by platform for Firefox and Thunderbird.
Before doing that, you will probably want to go to the Windows Tools | Folder Options | View menu and uncheck the box that says "Hide extensions for known file types" so that it will be easier to see the .js extension after you name the file.
Here are the steps to follow to create these files:
After the files have been created, you can edit and save them using your favorite text editor (Wordpad and Notepad are two possibilities if you are using Windows).
If you choose to set preferences by using user.js and later change your mind, there is a method that you will have to use to change these preferences back, because the changes are written to prefs.js (simply deleting the preferences from user.js won't cut it). You have to open a text editor and delete the preferences from prefs.js. The other (and easier) option is to edit them using about:config, which was explained previously.
Here is an example of a command that you could add to your user.js file to change the URL that the Throbber takes you to when you click it:
// Click on throbber to go to Thunderbird Help: user_pref("messenger.throbber.url", "http://texturizer.net/thunderbird/");
Many more examples of this kind can be found at http://www.mozilla.org/support/firefox/tips.