Following fixes: admin theme supports <button> tag now, PageProcessor can eval now, and SpecialAdmin.php plugin can no longer be disabled
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script language="javascript" src="../../tiny_mce_popup.js"></script>
<script type="text/javascript" src="jscripts/embed.js"></script>
<title>Example of a custom preview page</title>
<link href="{$content_css}" rel="stylesheet" type="text/css" />
</head>
<body>
Editor contents: <br />
{$content}
</body>
</html>