Firefox may repeatedly open new, empty tabs or windows after you click on a link, forcing you to close Firefox. The same untitled tabs or blank windows may open the next time you start Firefox, if the previous session is restored.

This usually happens because you chose Firefox as the program to always use for a particular action, such as opening a certain type of file or launching an application to send mail.

Start a new Firefox session

You may be forced to close Firefox if it is repeatedly opening multiple tabs or windows. Firefox includes a Session Restore feature that can restore your windows and tabs from the previous session after a crash or unexpected close.

The same multiple tabs or windows may start opening when you next start Firefox, forcing you to close Firefox again. If you see a Restore Session (i.e. "Well this is embarrassing") page when you restart Firefox, click Start New Session.

Once you start a new Firefox session, follow the instructions given below to fix the problem.

Change the action for a content type

You may be able to fix the problem by finding the content type that is set to use Firefox and then changing the action, using these steps:

1. At the top of the Firefox window, click on the Firefox button (Tools menu in Windows XP) and then click OptionsOn the menu bar, click on the Firefox menu and select Preferences...At the top of the Firefox window, click on the Edit menu and select PreferencesAt the top of the Firefox window, click on the Tools menu and select Options...On the menu bar, click on the Firefox menu and select Preferences...At the top of the Firefox window, click on the Edit menu and select Preferences...
2. Select the Applications panel.
3. If you know which item in the Content Types column is causing the problem, select it. Otherwise, in the Search box, type Use Firefox. The list will display only items that are set to "Use Firefox".
   
   
4. For each problematic content type, select a new action from the menu in the Action column. If you're not sure which action to pick, choose Always ask.
5. Click OK to close the Options windowClick Close to close the Preferences windowClose the Preferences window .

For general information on content types, see Managing file types.

Reset actions for all content types

If the preceding steps didn't fix the problem, or if you can't find the problematic item in the Applications list, you will have to reset the actions for all content types, by manually deleting the file that stores these settings.

1. Open your profile folder:

   1. At the top of the Firefox windowOn the menu bar, click on the Help menuAt the top of the Firefox window, click on the Firefox button, go over to the Help menu (on Windows XP, click on the Help menu)On the menu bar, click on the Help menuAt the top of the Firefox window, click on the Help menu and select Troubleshooting Information. The Troubleshooting Information tab will open.
   2. Under the Application Basics section, click on Open Containing FolderShow in Finder. A window with your profile filesfolder will open.
      Note: If you are unable to open or use Fire​fox, follow the instructions in Finding your profile without opening Firefox.

2. Close Firefox. 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.
3. Delete the file named mimeTypes.rdf.
4. Restart Firefox.