function startList() {

    navRoot = document.getElementById("menu");
    for (i = 0; i < navRoot.childNodes.length; i++) {
        node = navRoot.childNodes[i];
        if (node.nodeName == "LI") {
            node.onmouseover = function() {
                this.className += " over";
            }
            node.onmouseout = function() {
                this.className = this.className.replace(" over", "");
            }
        }
    }
}

window.onload = startList;