javascript - unsafeWindow is not defined

Question

My code is:

var $ = unsafeWindow.$, jQuery = $;
$('head').append('<link type="text/css" href="http://twitterchat.p.ht/chatstyle.css" rel="stylesheet" charset="utf-8"><script type="text/javascript" src="http://twitterchat.p.ht/wp-content/plugins/envolve-chat/envolve_api_client.php" charset="utf-8"></script><script type="text/javascript" src="http://twitterchat.p.ht/wp-content/plugins/envolve-chat/envolve-chat.php" charset="utf-8"></script>');

But the problem is that it has one error. I need help with this script. I'm new on javascript.

Thanks.