var activeimage="";

function doclick(ID)
{
if (activeimage!="") 
{
  domstyle(activeimage).visibility='hidden';
  domstyle("thumb_"+activeimage).className="thumbnail";
}
domstyle(ID).visibility='visible';
if (document.getElementById("thumb_"+ID)){
  domstyle("thumb_"+ID).className="thumbnail_active";
}
activeimage=ID;
}