if (mtDropDown.isSupported()) {
		var ms = new mtDropDownSet(mtDropDown.direction.down, 0, 0, mtDropDown.reference.bottomLeft);
		var menu1 = ms.addMenu(document.getElementById("menu1"));
		menu1.addItem("- 水源热泵","about.asp"); // send no URL if nothing should happen onclick
		menu1.addItem("- 土壤源热泵","zzjg.asp");
		mtDropDown.renderAll();
	}