Firefox automatically adds a print header and footer when printing websites which is something that most users do not want. By default, page title and URL as well as the page number and time / date are added to each page that gets printed. It is not that obvious but it is possible to customize the printout.
One option that might appeal to many users is to disable the header (Title and URL) and footer (page number and time / date) completely. The locations left, center and right can be customized for the header and footer of every printed page. It is possible to set those locations to blank if you do not want to add information about the page in the printout or configure it to contain any of the following variables: Title, URL, Page #, Page # of #, Date/Time and custom.
Any kind of text can be added in a custom field if you choose that one, the rest should be self explanatory. Besides configuring header and footer options it is possible to configure page margins, orientation, scale and if you want to print background images as well.

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It might seem obvious, but it would help if you said where these options can be found.
Thanks for this.
PS: Page Setup options can be found under the File menu.
…except when I choose Page Setup from the File menu, I get an extremely simple popup with absolutely none of those options. It just lets me choose printer, paper size, portrait/landscape and flipping.
None of the options for margins and headers and footers are present.
(Firefox 3.6.12 on Ubuntu Linux)
have the same problem as James Paige (Firefox 3.6.13 on Ubuntu 10.10)
I found an answer here: http://support.mozilla.com/en-US/questions/694950#answer-15676 regarding how to configure for ubuntu (manually)