I installed the Firemacs Firefox add-on for making Firefox respond to Emacs shortcuts, but I ended up removing it: it seems that I’ve spent so long down-translating my fingers on non-Emacs applications like Firefox that it’s easier to continue that way than to change to using the keyboard properly (or “like god intended” as Norman Walsh put it at Mind you, I’ll probably enable it again after the next time that I use C-n in a text box in the browser.