function PopupCentrata(URL,w,h) {
   var l = Math.floor((screen.width-w)/2);
   var t = Math.floor((screen.height-h)/2); 
   var stili = "top=" + t + ", left=" + l + ", width=" + w + ", height=" + h + ", status=no, menubar=no, toolbar=no scrollbar=no";
   var testo = window.open(URL, "", stili);
}