if (mtDropDown.isSupported()) {

		var ms = new mtDropDownSet(mtDropDown.direction.down, 0, 0, mtDropDown.reference.bottomLeft);
//第二菜单
		var menu3 = ms.addMenu(document.getElementById("menu3")); 
		menu3.addItem("<li> 企业简介", "introduction.asp");
		menu3.addItem("<li> 企业文化", "culture.asp"); 
		mtDropDown.renderAll();
	}