function rollover() {
    if (!document.getElementById || !document.createTextNode) { return; }
    var n = document.getElementById('TopNavigation');
    if (!n) { return; }
    var lis = n.getElementsByTagName('li');
    for (var i = 0; i < lis.length; i++) {
        lis[i].onmouseover = function() {
            this.className = this.className ? 'active' : 'over';
        }
        lis[i].onmouseout = function() {
        this.className = this.className == 'active' ? 'active' : '';
        }
    }
}
window.onload = rollover;