ieHover = function() {
    var lis = document.getElementById("header").getElementsByTagName("li");
    for (var i=0; i<lis.length; i++) {
        lis[i].onmouseover=function() {
            this.className+=" over";
            //alert(this.className);
        }
        lis[i].onmouseout=function() {
            this.className=this.className.replace(new RegExp(" over\\b"), "");
        }
    }
}
if (window.attachEvent) window.attachEvent("onload", ieHover);