Options for Linux), there are other hidden potential, as well as Firefox and Thunderbird Mozilla Suite.

Preference is a value or a program of behavior that can be changed. Preferences changed via the user interface (via the Options panel) generally take effect immediately and are stored in the prefs.js file in your profile. However it is strongly recommended to edit this file, use the file user.js prefer

The user.js file is located in your profile folder, as prefs.js but it is not created by default. If it does not exist, simply create a text file with a text editor such as Notepad, emacs or vi, and save it under the name user.js Make sure it is in the same folder as the file prefs.js.

Whether Firefox, Thunderbird, Mozilla Suite or Nvu, Gecko software never alter the file contents user.js Conversely, the contents of prefs.js is frequently updated. If you directly modify the prefs.js file it is possible that the next application launch your changes disappear.

Note: You can also change your preferences via the panel about: config, in this case the changes will be directly stored in the prefs.js files but we’ll get to that later.

To undo changes made by the file user.js you can not just remove preferences included in the file because they remain stored in the prefs.js file. You will have to also delete the entry in the prefs.js file using a text editor or using about:config.
What user.js look like?

Your preferences should use the « user_pref » as written in the example below.

You can post comments in the user.js file to describe its content, like any JavaScript file. To create a comment, you must skip a line and precede your text by two slashes : //. If your comment takes into multiple lines, you must precede each line with two slashes or frame your text with symbols /* et */.

Examples of preferences as well as their function. They can be copied as is in your file user.js.

The user_pref () command – here in blue – accepts two arguments separated by commas. The first argument – in red – is the name of the preference, which must be quoted. Then the second argument – purple – can be of three forms:
– Boolean: can be set either true or false (that is to say either true or false);
– A whole: one can put only integers, usually positive or zero, but not necessarily. Examples: -1, 0, 1, 2, etc. ;
– A string: you can put any sequence of characters, it often has to be a URL. Exemple : http://www.geckozone.org

Now that you know the syntax of preferences, go to another method where you must use about: config. This is a special address, you must type in the address bar instead of that of a website. Do so and the list of hidden preferences appear.

If preferences are bold, is that their values ??are not the default ones. It is possible that they were modified by changes in the Options panel or by extensions.

To change a preference simply right-click it, click on “Edit” in the menu that appears simpler … Or, double-click on the line and the edit window will appear if is a string or an integer. For a boolean, double-click the reverse.