// https://bugzilla.mozilla.org/show_bug.cgi?id=329601
document.getElementById('navigator-throbber').onclick = function(event)
  {
    if (event.button == 0) {
      var uri = null;

      try {
        uri = gPrefService.getCharPref('browser.throbber.url');
      } catch(e) { }

      if (uri)
        loadURI(uri, null, null, false);
    }
  };