Hi, from Firefox 41, you need to use the add-on New Tab Override (browser.newtab.url replacement), to make changes to the New Tab page.

Once installed, open the Add-ons Manager (Ctrl+Shift+A) > Extensions, then look for New Tab Override and click on Options to set your preference.

Note, if you only want the New Tab to be the same as your Home page, you can use the add-on New Tab Homepage instead.

You may then need to restart Firefox for any changes to take effect.

To use Super Start, you can try this: Type about:config into the address bar, press Enter, accept the warning, scroll down to extensions.superstart.set.browser.newtab.url and double click to change 'Value' from False to True, then restart Firefox.

If your question is resolved by this or another answer, please take a minute to let us know. Thank you.

Issue solved. Thank you. Solution is not so easy, hard to understand what to do by yourself! I was thinking problem with superstart app and re-installed it. And it is good, what I had a backup for my superstart. Before that I was happy with firefox, now - I`m not. It was a bad surprise.

Note that for Super Start you can use the about:superstart page to set as the new tab page.