We're using a small and useful function to convert event of any supported browser into our own internal event object (thus we do not need to deal with multiple browsers every time when we need to handle some event).
For your case, you just need to get the key code for the keydown event:
function FTVonkeydown(event)
{
var keycode = window.event ? window.event.keyCode : event.which;
//and then switch through values that you need to handle:
//for example in case of DOWN button keycode is 40
// if no suitable keycode found - return true so default action will proceed.
// otherwise - return false and call event.preventDefault()
}
like this.