function opensub(item_id){
 var menu_line = document.getElementById("dv"+item_id);
 var img_line = document.getElementById("arrow"+item_id);
 if(menu_line.style.display=="none"){
  menu_line.style.display="block";
  img_line.className = "minus";
  return;
 }
 else{
  menu_line.style.display="none";
    img_line.className = "plus";
 }
}