(document.layers) ? layerobject=true : layerobject=false;
(document.all) ? allobject = true: allobject = false;
(document.getElementById) ? dom = true : dom = false;

function changeVisibility(id,action)
{
 switch (action)
{
   case "show":
      if (layerobject)
            document.layers[''+id+''].style.visibility = "show";
         else if (allobject)
            document.all[''+id+''].style.visibility = "visible";
         else if (dom)
            document.getElementById(''+id+'').style.visibility = "visible";
         break;

   case "hide":     
         if (layerobject)
            document.layers[''+id+''].style.visibility = "hide";
         else if (allobject)
            document.all[''+id+''].style.visibility = "hidden";
         else if (dom)
            document.getElementById(''+id+'').style.visibility = "hidden";
         break;
   default:return;
 }
   return;   
}