I've created a CSP page to take in a base64 value from a <textarea> and decode it. When I run it I get the error . Any ideas?

Error: <ILLEGAL VALUE>zOnPageBODY+28^csp.decode.1

ErrorNo: 5002

Here is my code

<form method="post" action="">
<table>
<tr><td><textarea rows="40" cols="200" name="submitstring"></textarea></td></tr>
<tr><td><select name="decodeoption"><option>Decode</option><option>Encode</option></select><input type="submit"/></td></tr>
<tr><td>&nbsp;</td></tr>
<tr><td><h2>Result</h2></td></tr>
<tr><td>
<script language=Cache runat=server>
Set tString = $Get(%request.