var sfHover = function() {
	var sfEls = document.getElementById("nav").getElementsByTagName("LI");
	for (var i=0; i<sfEls.length; i++) {
		sfEls[i].onmouseover=function() {
			this.className+=" sfhover";
		}
		sfEls[i].onmouseout=function() {
			this.className=this.className.replace(new RegExp(" sfhover\\b"), "");
		}
	}
}
if (window.attachEvent) window.attachEvent("onload", sfHover);

function showParent(layer) {
    var l = document.getElementById(layer);
    // Hieronder kan vast beter...
    var pl = l.previousSibling;
    alert(pl.id);

    //var p = document.getElementById(pl);
    //p.style.backgroundColor = "#FF0000";
}

function hideParent(layer) {
    var l = document.getElementById(layer);
    // Hieronder kan vast beter...
    var pl = l.parentNode.firstChild.id;
    var p = document.getElementById(pl);
    p.style.backgroundColor = "#F0F0F0";
}