function showLayer(layerName){
  if (document.getElementById) {
    // Level 1 DOM code
	eval('document.getElementById("'+layerName+'").style.visibility="visible"');
   }
   else if (document.all) {
    // Microsoft DOM code
	eval('document.all["'+layerName+'"].style.visibility="visible"');
   }
   else if (document.layers) {
    // Netscape DOM code
	eval('document.layers["'+layerName+'"].visibility="visible"');
   }
}	
function hideLayer(layerName){
  if (document.getElementById) {
    // Level 1 DOM code
	eval('document.getElementById("'+layerName+'").style.visibility="hidden"');
   }
   else if (document.all) {
    // Microsoft DOM code
	eval('document.all["'+layerName+'"].style.visibility="hidden"');
   }
   else if (document.layers) {
    // Netscape DOM code
	eval('document.layers["'+layerName+'"].visibility="hidden"');
   }
}