function changeImage(newImage){
	img = new Image();
	img.src= newImage;
	return img.src;
	
}
function showLayer(layerName){
  var elms,thiselm,img;
  elms = document.getElementsByTagName("div");
  for (var i=0;i<elms.length;i++) if(elms[i].id) elms[i].className="hidden";
  elms = document.getElementsByTagName("img");
  for (var i=0;i<elms.length;i++) if (elms[i].id) elms[i].src="html/piazzamercato/img/arrow_menu_off.jpg";
  
  thiselm = document.getElementById("layer_"+new String(layerName));
  thiselm.className = "show"; 
  thiselm = document.getElementById("img_"+new String(layerName));
  thiselm.src ="html/piazzamercato/img/arrow_menu_on.jpg";
  
}

var imgon = new Image();
var imgoff = new Image();
imgon.src="html/piazzamercato/img/arrow_menu_on.jpg";
imgoff.src="html/piazzamercato/img/arrow_menu_off.jpg";