Preferences not saved
This article deals with Firefox or Mozilla Suite not saving any changes made to options or preference settings after you restart the application. If only Firefox toolbar customizations are not being saved, see this article.
Read-only preference file
The inability to save any preference changes can be caused by having the prefs.js or "prefs.js.moztmp" file in the profile folder set to read-only. You may receive an error similar to "Failed to save the preferences file. Any preference changes will be lost at the end of the session" [1]. You may also find multiple files named "prefs-n.js" (where n is a number) appearing in the profile folder.
Check the file properties of the prefs.js file and any "prefs.js.moztmp" file found and remove the "read-only" attributes to resolve the issue.
Note that other read-only files in the profile folder can cause similar problems, for example, a read-only cookies.txt or "cookies.txt.moztmp" file can cause loss of cookie data and creation of multiple cookies files and a read-only bookmarks.html or bookmarks.html.moztmp file can cause bookmarks not to be saved (see bookmarks not saved) and creation of multiple bookmarks files.
Dell Network Assistant
Dell Network Assistant may also cause this problem. If you have this program, try uninstalling it.[2]
User.js file locks certain preferences
If you are able to change some preference settings but not others, look for a user.js file in your profile folder (Windows users, read this). The user.js file does not exist by default; it is created by users and, in a few cases, by some software programs, so that certain settings get written back to the prefs.js file each time you restart Firefox or Mozilla Suite. If you find a user.js file, either remove it from the profile folder or edit the file to remove any unwanted settings. See the article Resetting preferences for more information.
Related bugs
- Bug 157152 - read-only/hidden bookmarks.html (or bookmarks.html.moztmp) causes creation of bookmarks-{n+1}.html
- Bug 257288 - read-only profile files (cookies, bookmarks, etc) not respected, results in data loss
