Before installing this add-on I was a bit concerned by quite a few of the reviews saying it didn't work or was complicated to use.
Well, it worked perfectly for me, and was not in any way complicated. If you simply wish to set your newtab to open on a fixed webpage, go to the add-on options and type the desired URL into the text box. Done. It's that simple.
It's a bad reflection on Mozilla that this add-on is needed, but a huge thanks must go to the developer for creating it.
Mozilla really should have known better than to force a change so radical upon their userbase that it requires an add-on to return things to normality.