<!DOCTYPE HTML>
<html>
<head>
*!*<script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.js"></script>*/!*
</head>
<body>
<a href="#" onclick="*!*$('#block').slideDown(3000);*/!*return false;">Показать</a>
<div id="block" style="width: 100px;height: 100px;background:red;display: none;"></div>
</body>
</html>