document.onkeyup = controleerToets;

function controleerToets(e)
{
	var KeyID = (window.event) ? event.keyCode : e.keyCode;
	
	switch(KeyID)
	{
		case 37:
		if (document.getElementById('vorigeLink'))
		{
			document.location.href = document.links[3].href;
		}
		break;
		
		case 39:
		if (document.getElementById('volgendeLink'))
		{
			document.location.href = document.links[4].href;
		}
		break;
	
	}
}