function init() {			
			if (mtDropDown.isSupported()) {
				mtDropDown.initialize();				
			}
}	

/**
*菜单的构造,需要绑定到onload
*/
startList = function() {
    if (document.all&&document.getElementById) {
        navRoot = document.getElementById("nav");
            for (i=0; i<navRoot.childNodes.length; i++) {
                node = navRoot.childNodes[i];
                if (node.nodeName=="LI") {
                    node.onmouseover=function() {
                    this.className+=" over";
                }
                node.onmouseout=function() {
                    this.className=this.className.replace(" over", "");
                }
            }
        }
    }
}