In Firefox 41 that '''browser.newtab.url''' pref is gone. That pref was being hijacked by malware so frequently so Mozilla decided to remove that pref to eliminate that type of hijack. You will need an extension such as this to restore it. https://addons.mozilla.org/en-US/firefox/addon/new-tab-override/ Or for having your homepage as the new tab page, try this extension. https://addons.mozilla.org/en-US/firefox/addon/new-tab-homepage/ If you are using Classic Theme Restorer, go into CTR options > General UI (2) and set your preference for the new tab URL there. For [https://addons.mozilla.org/en-US/firefox/addon/super-start/?src=ss Super Start] you can use the '''about:superstart''' page.