Sorry to hear about the freezes. I'm not sure what kind of error you are seeing. Is there any additional information in the message?

It might help to provide a screenshot of the message if you can't copy/paste from it. This article has tips on that: How do I create a screenshot of my problem? Please cut out or blur any sensitive information in the image before attaching the file to a reply.

If this is associated with particular web pages, it could be a popup solicitation trying to convince you to download/install something bad. Do you notice any pattern like that?

If this appears randomly, it could be a problem created by one of your add-ons. Could you test in Firefox's Safe Mode? In Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement? (More info: Diagnose Firefox issues using Troubleshoot Mode)

By the way, here are some ways to try to close a "bad tab":

• Ctrl+w or Ctrl+F4 (close tab)
• Alt+F4 (close window)
• hover the Firefox icon on the task bar and try the little red X button on the thumbnail image of the tab
• right-click the Firefox icon on the task bar and choose Close Window or Close All Windows (whichever one is available)