As a Windows user, I'm not sure this is how it works on Mac, but please take a look. (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button promising to be careful. (2) In the search box above the list, type or paste '''print*header''' and pause while the list is filtered (3) There are a lot of entries: there is a headercenter, headerleft, and headerright representing the default and the same three for each printer Firefox discovered on your system. The '''&T''' placeholder is the title, and the '''&U''' placeholder is the URL. To edit a preference, double-click it, and then you can remove the unwanted placeholder. (4) In the search box above the list, type or paste '''print*footer''' and pause while the list is filtered (5) Repeat step #3 for footercenter, footerleft, and footerright. If you switch to a normal web page to test, does that work? Does it stick from job to job?