There are several possible explanations for this annoying situation. (1) Please see our support article, particularly the section on a possible, optional, user.js file in your settings (profile) folder: [[How to fix preferences that won't save]]. ''By default, Windows hides the .js extension, so if you see a file named user with a type of JScript, that's most likely the user.js file. Or to make it easier, set Windows to show all file extensions using the steps in this article: [http://windows.microsoft.com/en-us/windows/show-hide-file-name-extensions].'' (2) If you use Advanced SystemCare, or another security/privacy/utility program that prevents unwanted changes to browser settings (sometimes called home page protection), try disabling that until you have Firefox working properly. Otherwise, the program will keep undoing your changes. (3) Investigate possible malware, or at least a bad add-on. Here's my suggested procedure for tracking down and cleaning up bad add-ons. I know it seems long, but it's not that bad. (A) Open the Windows '''Control Panel''', Uninstall a Program. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install. ''Be suspicious of everything you do not recognize/remember, as malware often uses important or innocent sounding names to discourage you from removing it.'' Take out as much trash as possible here. (B) Open Firefox's '''Add-ons page''' using either: * Ctrl+Shift+a * "3-bar" menu button (or Tools menu) > Add-ons * in the Windows "Run" dialog, type or paste <br><code>firefox.exe "about:addons"</code> In the left column, click '''Plugins'''. Set nonessential and unrecognized plugins to "Never Activate". In the left column, click '''Extensions'''. Then, if in doubt, disable (or Remove, if possible) unrecognized and unwanted extensions. ''Bear in mind that all extensions are optional; none ship with Firefox.'' Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step. Any improvement? (C) You can search for remaining issues with the '''scanning/cleaning tools''' listed in our support article: [[Troubleshoot Firefox issues caused by malware]]. These on-demand scanners are free and take considerable time to run. If they finish quickly and especially if they require payment, you may have a serious infection. I suggest the specialized forums listed in the article in that case. Success?