麻烦各位帮忙看看！急！下面的js，在firefox 中没有反应（在IE中没有问题）

var menuids=["boyicss"]
//显示下拉菜单
function submenus()
{
for(var i=0;i<menuids.length;i++)
{
var ultags=document.getElementById(menuids[i]).getElementsByTagName("ul")
for(var t=0;t<ultags.length;t++)
{
if(ultags[t].parentNode.parentNode.id==menuids[i])
{
ultags[t].style.top=ultags[t].parentNode.offsetHeight+"px"
ultags[t].parentNode.getElementsByTagName("a")[0].className="mainfoldericon"

}
else
{
ultags[t].style.left=ultags[t-1].getElementsByTagName("a")[0].offsetWidth+"px"
ultags[t].parentNode.getElementsByTagName("a")[0].className="subforldericon"
}
ultags[t].parentNode.onmouseover=function(){
this.getElementsByTagName("ul")[0].style.visibility="visible"
}
ultags[t].parentNode.onmouseout=function(){
this.getElementsByTagName("ul")[0].style.visibility="hidden"
}
}

}
}
if(window.addEventListener)
{
window.addEventListener("load",submenus,false)

}
else if(window.attachEvent)
{
window.attachEvent("onload",submenus)
}

fribug 单步调试