protected function renderCss()
    {
        $html = "";

        foreach( $this->css as $item )
        {
            $html .= sprintf( MPageController::CSS_TEMPLATE, $item["rel"], $item["href"], $item["media"] ) . "\n";
        }

        $domQuery = $this->qp->find( "head" );
        if( $domQuery->count() <= 0 )
        {
            trigger_error( 'head tag not found in page', E_USER_WARNING );
        }
        else
        {
            $domQuery->append( $html );
        }
    }