With Firefox 41 (and higher), it's no longer possible to customize the page shown in a new tab via changing the preference browser.newtab.url in about.config. Because of the fact that hijackers abused the preference in the past, Mozilla decided to remove it (see bug 1118285). Fortunately, by removing it, Mozilla also introduced a new API to bring this functionality back to life as an add-on. This add-on allows the user to choose a certain page in a new tab. New Tab Override (browser.newtab.url replacement) https://addons.mozilla.org/en-US/firefox/addon/new-tab-override/ This is also available using '''[https://addons.mozilla.org/en-US/firefox/addon/classicthemerestorer/ Classic Theme Restorer (Customize Australis)]''' {web link} Restore squared tabs, appmenu, add-ons bar, small button view and more on Australis UI (Windows/MacOSX/Linux + Fx 29+). ----------- Have you checked for an update for what you were using before? What is it called? Not what you were looking for, but . . . '''[https://addons.mozilla.org/en-US/firefox/addon/customizable-shortcuts/ Customizable Shortcuts]''' {web link} Allows to customize Firefox shortcuts.

Thanks for your notes. The customizable shortcut link that you provided is the one that I was using, which appears to have 'broken' with FF42. Too bad, because I often fat finger some combination of keys

Check with it's support site.

You can also look at keyconfig. *http://dorando.emuverse.com/projects/mozilla/readme.html