Could you describe the steps that cause this to happen, for example: * Starting Firefox up * Opening a new window (Ctrl+n) * Opening a new tab (Ctrl+t) * Double-clicking the Firefox home page shortcut after Firefox is already running ---- Your "More System Details" shows that there is an optional settings file named user.js in your current active personal settings (profile) folder. Firefox reads this file at startup and uses it to override your previous session settings. Unless you created that file yourself, it may contain unwanted instructions. This article has a section on how to track it down and remove it: [[How to fix preferences that won't save]]. Note: By default, Windows hides the .js extension on files, so if you see a file named user of type JScript, that is the user.js file.