code: private final void error(String message, CharSequence identifier) {
      if (badHtmlHandler != Handler.DO_NOTHING) {   // Avoid string append.
        badHtmlHandler.handle(message + " : " + identifier);
      }
    }
docs: Called when the series of calls make no sense.
  May be overridden to throw an unchecked throwable, to log, or to take some
  other action.
  
  @param message for human consumption.
  @param identifier an HTML identifier associated with the message.