In some instances, Firefox may not remember changes you've made to your toolbar settings or certain other configuration changes.

This article explains how to fix the underlying problem that may result in one or more of the following symptoms:

• Changes that you made to your toolbars are not saved when you restart Firefox.
• Changes made to the browser window's size and position are not remembered when you restart Firefox.
• You cannot save new bookmarks.

Causes

The above symptoms are usually caused by a corrupted file in your Firefox user data, called localstore.rdf. This file is maintained by Firefox to manage some of your configuration settings.

Another possible cause is a misbehaving Firefox extension.

Fixing the problem

Resetting localstore.rdf

1. At the top of the Firefox windowOn the menu bar, click the Help menuFirefox button, go over to the Help menu and select Restart with Add-ons Disabled.... Firefox will start up with the Firefox Safe Mode dialog.
   For Windows XP, click the Help menu and select Restart with Add-ons Disabled.... Firefox will start up with the Firefox Safe Mode dialog.

   Note: You can also start Firefox in Safe Mode by holding down the shift key while starting Firefox.holding down the option key while starting Firefox.quitting Firefox and then going to your Terminal and running: firefox -safe-mode
   You may need to specify the Firefox installation path (e.g. /usr/lib/firefox-4)
   At the top of the Firefox window, click on the Firefox button (File menu in Windows XP) and then click ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select QuitAt the top of the Firefox window, click on the File menu and select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit. Then in Windows, click Start, open the All Programs list and navigate to the Mozilla Firefox folder. In the Mozilla Firefox folder, select Mozilla Firefox (Safe Mode).Then hold down the option key as you restart Firefox.Go to your Terminal and run: firefox -safe-mode
   You may need to specify the Firefox installation path (e.g. /usr/lib/firefox-3.5). Firefox will start up with the Firefox Safe Mode dialog.
   Note: You can also start Firefox in Safe Mode by clicking Start, selecting Run (or use the Start Search box in Windows 7 and Vista) and then entering the following in the text field: firefox -safe-mode
2. In the Firefox Safe Mode dialog, select Reset toolbars and controls and click Make Changes and Restart.
   
   
   

You should now be able to customize your toolbar settings and controls, change the browser window size or position, and save new bookmarks, and those changes will be remembered when you restart Firefox.

Disabling extensions

If the previous solution did not help, you can temporarily disable all extensions and then restart Firefox. If the symptoms go away then one of your extensions was causing the problem. For more information, read Troubleshooting extensions and themes.

Based on information from Corrupt localstore.rdf (mozillaZine KB)