protected function addScript($script,$options=array(),$at='begin')
    {
        $options["type"] = Utility::get($options, "type", "text/javascript");
        $this->tags[md5($script)] = array(
            "at"=>$at,
            "tag"=>"script",
            "options"=>$options,
            "content"=>$script,
        );
        return $this;
    }