// JavaScript Document
function ventanaNueva(theURL, winName, ancho, alto, features) {
//  alert(screen.width);
  features += ",left=" + ((screen.width - ancho) / 2);
  features += ",top=" + ((screen.height - alto) / 2);
  features += ",width=" + ancho;
  features += ",height=" + alto;
  window.open(theURL, winName, features);
}