Is there a way to customize hotkeys in firefox?

[CrazyQwert]

I wanted to use a Alt + 7 (Numpad) to generate an "Alt-code" but this combination always leads me to the firefox start page what is kind of annoying, so I wanted to turn those keyboard-shortcuts of or at least remap them but I cant find an option for this in the settings 

[cor-el · Accepted solution]

Make sure that Num Lock is turned on, otherwise the 7 key behave as Home like printed on it.

[CrazyQwert]

Thank you very much