document.onkeydown = NavigateThrough;

function NavigateThrough(){
	link = 0;
	switch (event.keyCode ? event.keyCode : event.which ? event.which : null){
		case 0x25:
			link = document.getElementById ('link_left');
			break;
    case 0x26:
			link = document.getElementById ('link_up');
			break;
		case 0x27:
			link = document.getElementById ('link_right');
			break;
		case 0x28:
			link = document.getElementById ('link_down');
			break;
	}
	if (link && link.href) document.location = link.href;
}