function layer_show(layer_name,action){
if(action=="show"){
   document.getElementById(layer_name).style.visibility="visible";
}
else if(action=="hide"){
   document.getElementById(layer_name).style.visibility="hidden";
}
}

function change(_id)
{
 var ids= new Array();
 ids=["show3","show4","show5","show6"];
 var z=10;
 for(var i=0; i < ids.length; i++)
 {
  if(_id== ids[i])
  {
   document.getElementById(ids[i]).style.zIndex=(z+i);
  }
  else
  {
   document.getElementById(ids[i]).style.zIndex=(z-i);
  }
 }
}

function layer_show(layer_name,action){
if(action=="show"){
   document.getElementById(layer_name).style.visibility="visible";
}
else if(action=="hide"){
   document.getElementById(layer_name).style.visibility="hidden";
}
}