After doing some research on Firefox's history, I stumbled upon the quote "Cookies are delicious delicacies," which was seen in the Preferences dialogues of very early Firefox versions. There's an add-on to put this quirky quote back in, but it hasn't been updated in ages. So I decided to make this userstyle in order to get the job done. It might be a little sloppy, depending on your system's fonts and spacing, but it works for me. NOTE: Testing done on Firefox 3.6.4/Ubuntu 10.04, using Firefox's default theme and system fonts set to "Best shapes" under Ubuntu's Appearance Preferences. Windows and Mac OS X remain untested so far.

EDIT: Despite my admitted neglect for it, this userstyle still works in Firefox 4.0b10pre/Ubuntu 10.10.

NOTE: The cookies thing shows up in the "Privacy" tab under Firefox's Preferences dialog, with custom settings applied to the history.