window.onload=function(){
var Nav=document.getElementById("topmenu");
var lis=Nav.getElementsByTagName("li");
for(var i=0;i<lis.length;i++){
lis[i].onmouseover=function(){
var subMenu = this.getElementsByTagName("ul")[0];
subMenu.style.display = "block";}
lis[i].onmouseout=function(){
var subMenu = this.getElementsByTagName("ul")[0];
subMenu.style.display = "none";}}}