var  currentLayer= '';

function setCurrentLayer(layer) {
	
 if(layer == currentLayer)
	return;
	
 if (document.layers) {
         document.layers[layer].visibility='show';
		
	     if(currentLayer != '')
		 {
			 document.layers[currentLayer].visibility='hide';
			 
		 }
   }
   else if (document.all) {
      document.all(layer).style.visibility='visible';
	  
	  if(currentLayer != '')
	  {
      	document.all(currentLayer).style.visibility='hidden';
	  }
	  
   }
   else if (document.getElementById) {
      document.getElementById(layer).style.visibility='visible';
	  if(currentLayer != '')
	  {
		  document.getElementById(currentLayer).style.visibility='hidden';
  		  
	  }
   }
   currentLayer = layer;
}