function menu_change(class_id,img_id){
	var obj = "";
	var img = "";
	obj = document.getElementById(class_id);
	img = document.getElementById(img_id);
	if(obj.className == "dis_open"){
		obj.className = "dis_close";
		img.src = img.src.replace("_op.", "_cl.");
	}else{
		obj.className = "dis_open";
		img.src = img.src.replace("_cl.", "_op.");
	}
}