function navigate(event) {
	if(!document.getElementById) return;

	if(window.event) event = window.event;

	if(event.ctrlKey) {
		switch(event.keyCode ? event.keyCode : event.which ? event.which : null) {
			case 0x25:
				if(document.getElementById("prevlink")) document.location = document.getElementById("prevlink").href;
				break;
			case 0x27:
				if(document.getElementById("nextlink")) document.location = document.getElementById("nextlink").href;
				break;
			case 0x26:
				if(document.getElementById("uplink")) document.location = document.getElementById("uplink").href;
				break;
			case 0x28:
				if(document.getElementById("downlink")) document.location = document.getElementById("downlink").href;
		}
	}
}

document.onkeydown = navigate;