event.shiftKey may enable you to distinguish between capital and lowercase - depending on the key event you use (I haven't clarified this fully but believe this applies to keydown). You then could use toLowerCase()
to output the correct character, or add 32 to the key-code.
..depends on what key was pressed..
I always use Backspace to return to the previous page (Back) - on all browsers. To prevent this action you either need to return false
from your event (which should work on its own) or event.preventDefault()