-Showing and hiding alerts with jQuery functions slideUp() and slideDown()
-Classes ".alert", ".close" and ".btn" are used from bootstrap
-Remember including the necessary files, both bootstrap and jquery. Should be something like this:
<script src="bootstrap/js/jquery-1.7.2.min.js" type="text/javascript"></script>
<script src="bootstrap/js/bootstrap.js" type="text/javascript"></script>
<link href="bootstrap/css/bootstrap.css" rel="stylesheet" type="text/css" />