// JavaScript Document
<script type=text/javascript>
/**
*菜单的构造,需要绑定到onload
*/
startList = function() {
if (document.all&&document.getElementById) {
dropmenuRoot = document.getElementById("nav_main");
for (i=0; i<dropmenuRoot.childNodes.length; i++) {
node = dropmenuRoot.childNodes[i];
if (node.nodeName=="LI") {
node.onmouseover=function() {
this.className+=" over";
//开始灌水
for(j=0;j<this.childNodes.length;j++){
if (this.childNodes[j].nodeName=="UL"){
if (this.childNodes[j].childNodes[0].nodeName=="LI"){
if (this.offsetLeft+this.childNodes[j].childNodes.length*this.childNodes[j].childNodes[0].offsetWidth-dropmenuRoot.offsetLeft>dropmenuRoot.offsetWidth){
var len=this.childNodes[j].childNodes.length*this.childNodes[j].childNodes[0].offsetWidth; //菜单的长度
(len>dropmenuRoot.offsetWidth) ? this.childNodes[j].style.width=881+"px" : this.childNodes[j].style.width=len+"px"; //给ul设置宽度 如果子菜单比较多，大于容器的宽度，那么ul的宽度就是容器的宽度
len =this.offsetLeft+len-dropmenuRoot.offsetLeft-dropmenuRoot.offsetWidth;
(len>this.offsetLeft-dropmenuRoot.offsetLeft) ? this.childNodes[j].style.marginLeft=-(this.offsetLeft-dropmenuRoot.offsetLeft) : this.childNodes[j].style.marginLeft=-len+"px";
}
}
}
}
}
//灌水完毕
node.onmouseout=function() {
this.className=this.className.replace(" over", "");
}
}
}
}
}
window.onload=startList;
</script>

<script type="text/JavaScript">
<!--
function MM_jumpMenu(targ,selObj,restore){ //v3.0
  eval(targ+".location='"+selObj.options[selObj.selectedIndex].value+"'");
  if (restore) selObj.selectedIndex=0;
}
//-->
</script>