Hi, try this: Type about:config into the address bar, press Enter, accept the warning, scroll down to browser.newtab.url and make sure 'Value' is set to about:newtab (right click > Modify, to change it if necessary, taking care not to alter anything else). You may then need to restart Firefox.

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Type about:config<enter> in the address bar. If a warning screen comes up, press the Be Careful button. At the top of the screen is a search bar. Type browser.newtab.url This tells Firefox what to show when a new tab is opened. If you want, right click and select Modify. You can change the setting to;

about:home (Firefox default home page), about:newtab (shows the sites most visited), about:blank (a blank page),

or you can enter any web page or about: page you want.

The same instructions are used for the new window setting, listed as browser.startup.homepage.