var visibleElement
visibleElement = null

function ShowHide(element_id)
{
  if (visibleElement != null)
  {
    document.all[visibleElement].style.position = "absolute";
    document.all[visibleElement].style.left = -1000;
    document.all[visibleElement].style.top = -1000;
    document.all[visibleElement].style.visibility = "hidden";
  }
  document.all[element_id].style.position = "static";
  document.all[element_id].style.visibility = "visible";
  
  visibleElement = element_id
}