function popUp(pagina) {
   var w = 800;
   var h = 800;
   var l = Math.floor((screen.width-w)/2);
   var t = Math.floor((screen.height-h)/2);
      window.open(pagina,"","width=" + w + ",height=" + h + ",top=" + t + ",left=" + l + ",scrollbars=yes");
      //return false;
 }