anchor.diff:        html.write("<div class='dhtmlx_popup_title'>$header</div>");
       html.write("<div class='dhtmlx_popup_text'><span>$text</span></div>");
       html.write("<div class='dhtmlx_popup_controls'>");
  +    
  +    //Custom html validator
  +    _validator.allowElement("div", attributes: ["result"]);
     }
     
     String addButton(String text, String result){
  
positive.code:     if (html != null){
        //finalize html initialization
        html.write("</div>");
        _box.innerHtml = html.toString();
        html = null;
      }
         
      //just ignore second show call, if any
      if (_ready != null)
        return;
      
      document.body.children.add(_box);
      _position_box();
  
negative.code:   return box.show();
  }
  
  class MessageBox{ 
    DivElement _box;
    var _key_handler;
    StringBuffer html = new StringBuffer();
    Completer<String> _ready;
    NodeValidatorBuilder _validator = new NodeValidatorBuilder.common();
     
    static DivElement _modality;
    static void modality(bool mode){
      if (MessageBox._modality == null){
  