function update_user_box() {
  var user_box = document.getElementById ("facebookBox") ;

  // add in some XFBML. note that we set useyou=false so it doesn't display "you"
  user_box.innerHTML = "<span style='float:right;margin-left:10px;'>"
                     + "<fb:profile-pic uid='loggedinuser' size='square' facebook-logo='true'></fb:profile-pic>"
                     + "</span>"
                     + "<p>Bienvenido <strong><fb:name uid=loggedinuser useyou=false></fb:name></strong>.<br/>Estás conectado(a) con tu cuenta de <strong>Facebook</strong>.</p>"
                     ;
                     
  // because this is XFBML, we need to tell Facebook to re-process the document
  FB.XFBML.Host.parseDomTree();
}