private void backButtonInvoked(){
  final String backUrl=browserHistory.moveBack();
  setToolbarButtonState();
  isBackOrForwardInProgress=true;
  navigateToURL(backUrl);
}

private void backButtonInvoked ( ) { final String backUrl = browserHistory . moveBack ( ) ; setToolbarButtonState ( ) ; isBackOrForwardInProgress = true ; navigateToURL ( backUrl ) ; }
handler for the " navigate backward " button . navigate backward causes a navigation to the previous url listed in the history buffer .
