Some problems with Firefox are caused by extensions or themes. This article will help you determine whether an extension or theme is causing your problem and, if it is, how to make Firefox run normally again.
Hint: if you don't want to apply safe mode options to your usual Firefox working environment, use Profile Manager to create a separate working environment.
This article lists some extensions that are known to cause problems. There are hundreds of extensions, and most problems are not listed here. If you do not find the problem listed below, follow the steps outlined in the Standard diagnostic - Firefox article.
[ ] Don't ask at startup
- without a tick in the check box - is preferred.
(If you check that particular box, you may find it less easy to use your default profile.)
Firefox prompts you for the profile to use each time you start Firefox