magari evita di usare tutte le variabili pubbliche/globali ... tipo ID, lst e perfino la i
codice:
function menuEnable()  {
	for(var	
		i = 0,
		lstItem = document.getElementById("navigation").getElementsByTagName("div"),
		showLst = function(lst){return function(){lst.className = "show"}};
		i < lstItem.length;
		i++
	){
		lstItem[i].onmouseover = function()  {
			this.lst = (this.lastChild.tagName == "UL")?this.lastChild :this.lastChild.previousSibling;
			this.ID = setTimeout(showLst(this.lst), 500);
		}
		lstItem[i].onmouseout = function()  {
			clearTimeout(this.ID);
			this.lst.className = "hide";
		}
	};
};