Maybe this can help as it seems you changed the Firefox behavior:

Type in Firefox's address bar:

about:config

Agree that you will be careful if asked, then type:

browser.newtab.url

Change it to:

about:newtab , that is the actual default setting.

Try to use the SearchReset extension to reset some preferences to the default values.

• https://addons.mozilla.org/firefox/addon/searchreset/

Note that the SearchReset extension only runs once and then uninstalls automatically, so it won't show on the "Firefox > Add-ons" page (about:addons).

I Have changed the browser.newtab.url to about:newtab and it works until I restart firefox then about:newtab is always overwritten and replaced by string. Any solutions?

If you do not keep changes after a restart or otherwise have problems with preferences, see:

• http://kb.mozillazine.org/Preferences_not_saved