function mostrar() {
  obj = document.getElementById('popup_bienvenida');
  obj.style.display = (obj.style.display=='none') ? 'block' : 'none';
  document.getElementById('enla').innerHTML = (obj.style.display=='none') ? 'Ocultar' : 'Mostrar';
  load('popup_cerrar.php')
  //load="pagina.php" type="text/javascript" ; 
}