var menuids=["tree"]; 

function buildsubmenus()
{
    for (var i=0; i<menuids.length; i++)
    {        
        var ultags=document.getElementById(menuids[i]).getElementsByTagName("ul");
        
        for (var t=0; t<ultags.length; t++)
        {
            //ultags[t].parentNode.getElementsByTagName("a")[0].className="subfolderstyle";
            
            ultags[t].parentNode.onmouseover = function()
            {
                this.getElementsByTagName("ul")[0].style.display="block";
            }
            
            ultags[t].parentNode.onmouseout = function()
            {
                this.getElementsByTagName("ul")[0].style.display="none";
            }
        }
    }
}

if (window.addEventListener)
    window.addEventListener("load", buildsubmenus, false);
else if (window.attachEvent)
    window.attachEvent("onload", buildsubmenus);