Start Firefox in Safe Mode {web Link} by holding down the <Shift (Mac Options) > key, and then starting Firefox. Is the problem still there?

Still doesn't work.

Type about:config<enter> in the address bar. If a warning screen comes up, press the Be Careful button. This is where Firefox finds information it needs to run. At the top of the screen is a search bar. Type newtab

In order to better assist you with your issue please provide us with a screenshot. If you need help to create a screenshot, please see How do I create a screenshot of my problem?

Once you've done this, attach the saved screenshot file to your forum post by clicking the Browse... button below the Post your reply box. This will help us to visualize the problem.

Thank you!