/**
   * watch the historyTokens after the querystring#historyToken or you could say
   * querystring#[historyEvent|applicationState]
   */
  private void initHistoryObservations() {

    History.addValueChangeHandler(this);

    // first load
    Track.track("home");
  }
  public void onValueChange(ValueChangeEvent<String> event) {

    // get the querystring token
    String historyToken = History.getToken();

    // send to static method that will send the __utm.gif to google's server fro tracking
    Track.track(historyToken);
  }