Hi, this might be caused by one of your extensions. Hold down the Option key when you start Firefox to start in Safe Mode. More - [[Troubleshoot Firefox issues using Safe Mode]]. If it's OK in Safe Mode, disable any theme or extensions you have - 3-bar menu > Add-ons > Themes/Extensions and restart Firefox; then if it's OK, re-enable them one by one until you find the culprit. You may need to restart Firefox after enabling some extensions. Also, it's possible that for some reason some sites may have set themselves as your home page: Firefox is able to open multiple home pages with the URLs separated by a 'pipe' ('''|'''), so please see - [[How to set the home page]], and in 'Home Page,' make sure that in addition to your home page URL, there isn't anything else - if there is, just delete it. (the Firefox start page is '''about:home''' but you may have set a different one). If it's easier, you can just click on Restore to Default instead. ''If your question is resolved by this or another answer, please take a minute to let us know. Thank you!''