Your System Details list shows that you have a user.js file in the profile folder to initialize prefs each time Firefox starts. The user.js file is only present if you or other software has created this file and normally it wouldn't be there. You can check its content with a plain text editor (right-click: "Open with"; do not double-click). The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session. You can delete the user.js file if you didn't create this file yourself. You can use this button to go to the currently used Firefox profile folder: *Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder) *http://kb.mozillazine.org/Profile_folder_-_Firefox Windows hides some file extensions by default. Among them are .html and .ini and .js and .txt, so you may only see file name without file extension. You can see the real file type (file extension) in the properties of the file via the right-click context menu in Windows Explorer. ---- You can check the <b>browser.newtab.url</b> pref on the <b>about:config</b> page and set that pref to your preferred new tab page. * the default new tab page with the tiles is <b>about:newtab</b> * the default home page is <b>about:home</b> * for a blank page you can use <b>about:blank</b> The browser.newtabpage.enabled pref should be set to true to use the page set via browser.newtab.url as the new tab page. *http://kb.mozillazine.org/about:config See this article about the New Tab page (about:newtab): *https://support.mozilla.org/kb/new-tab-page-show-hide-and-customize-top-sites