document.captureEvents(Event.KEYPRESS)

function alert_keycode(e){
	if (e.which == 8)
	{
		location.href = document.getElementById( 'prev' ).href;
	}
	else if (e.which == 32)
	{
		location.href = document.getElementById( 'next' ).href;
	}
	else if (e.which == 96)
	{
		location.href = document.getElementById( 'toc' ).href;
	}
}
document.onkeypress=alert_keycode