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Rose Vines' favourite tips for making the most of Firefox and Thunderbird

Preference files
Within each user's profile in Mozilla and Firefox three user-editable files — user.js, userChrome.css and userContent.css — store user preferences, browser appearance settings and Web page display settings respectively. These files don't exist by default, so you need to create them. User.js is located in your profile folder; the other two files are stored in the Chrome sub-folder of your profile folder.

You may find sample preference files already exist in those folders. For example, there's often a userChrome-example.css in the Chrome sub-folder. If such a file exists, simply rename it by dropping -example. If there are no sample files, you'll have to create the files from scratch.

To create the files, navigate to the appropriate folder, right-click in a blank space and select New —> Text Document from the pop-up menu, then name the new file user.js, userChrome.css or userContent.css (click Yes when warned about changing the file extension). You can edit these files using Notepad or any text editor. Both user.js and userContent.css start off empty; in userChrome.css, start with the following lines:

/* Do not remove the @namespace line -- it's required for correct functioning */
/* set default namespace to XUL */
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

Unless you're a whiz with JavaScript, the easiest way to add your own preferences is to copy and paste tips you find online. A Google search for userChrome or userContent should turn up plenty to start with.