public function setContent( $content = NULL )
	{
		if( is_object( $content ) ){
			if( !method_exists( $content, '__toString' ) ){											//  content is not a renderable object
				$message	= 'Object of class "'.get_class( $content ).'" cannot be rendered';		//  prepare message about not renderable object
				throw new InvalidArgumentException( $message ); 									//  break with error message
			}
			$content	= (string) $content;														//  render object to string
		}
		$this->content	= $content;
	}