function openWindow(url, ancho, alto) {
    var ventana = window.open(url,'ventana' + (Math.round((Math.random()*9)+1)),'left=100,top=100,width='+ ancho+',height='+alto+',toolbar=0,resizable=0,menubar=0,location=0,directories=0,scrollbars=0,status=0');
     return false;
}