function checkOlderMobileOS( ) {
  var ua = navigator.userAgent;
  var uaindex;

  // determine OS
  if ( ua.match(/iPad/i) || ua.match(/iPhone/i) ) {
    userOS = 'iOS';
    uaindex = ua.indexOf( 'OS ' );
  } else if ( ua.match(/Android/i) ) {
    userOS = 'Android';
    uaindex = ua.indexOf( 'Android ' );
  } else {
    userOS = 'unknown';
  }

  // determine version
  if ( userOS === 'iOS'  &&  uaindex > -1 ) {
    userOSver = parseInt(ua.substr( uaindex + 3, 3 ).replace( '_', '.' ));
  } else if ( userOS === 'Android'  &&  uaindex > -1 ) {
    userOSver = parseInt(ua.substr( uaindex + 8, 3 ));
  } else {
    userOSver = 'unknown';
  }

  if ( userOS === 'iOS' && userOSver < 14 ) {
  	return true;
  } else if ( userOS === 'Android' && userOSver < 5 ) {
  	return true;
  }
  return false;

}