public function addCssFile($href,$options=array())
    {
        $options["type"] = Utility::get($options, "type", "text/css");
        $options["rel"] = Utility::get($options, "rel", "stylesheet");
        $options["href"] = $href;

        $this->tags[md5($href)] = array(
            "at"=>'begin',
            "tag"=>"link",
            "options"=>$options,
            "content"=>"",
        );
        return $this;
    }