function move(id)
{
  var menu = document.getElementById(id);
  if(!menu) return;
  var height = menu.step + parseInt(menu.style.height);
  if(height <= 0){
    height = 0;
    menu.style.display = "none";
  }
  if(height >= menu.maxHeight) height = menu.maxHeight;
  menu.style.height = height + "px";
  if(height == 0 || height == menu.maxHeight){
    clearInterval(menu.timerId);
    menu.timerId = null;
  }
}