public function render()
  {
    switch($this->method)
    {
      case PixelType::HTML:
        return $this->content;
      case PixelType::IFRAME:
        return $this->_renderIframe();
      case PixelType::IMAGE:
      case 'image':
        return $this->_renderImage();
      case PixelType::JS:
      case 'javascript':
        return $this->_renderJavascript();
      default:
        return null;
    }
  }