Solve the Problem of deleting a project that is incorrectly added to the about: config file in Firefox.

Method 1: Enter about: config in the address bar and press enter to enter the Variable list. Right-click the variable you want to delete and select "Reset". Restart ff. After that, enter about: config again and you will find that the variable has been deleted. In this case, you can create the correct variable by right-clicking the new variable in the menu.

Method 2: this approach is also substantive. The new variables added through about: config are saved in the FF Program System File.Prefs. js.
The file is located in the same folder, namely, c: \ Documents and
Settings \ ****** \ Application
Data \ Mozilla \ Firefox \ profiles \ 12345678. default. Open prefs. js in a text editor and you will find
About: the User-Defined variables in config are basically stored in this file. Find the project you want to delete and complete it as needed. You can delete it, you can also modify it directly. No
Note that these activities must be performed when FF is disabled. Otherwise, when FF is disabled, the project in this file will be rewritten by ff, the changes you made are in vain. After modification,
Save the file and open ff.