Javascript error

Hi

I'm not sure if this is a CMS Builder problem.

I get this javascript error:

Message: Object expected
Line: 1
Char: 1
Code: 0
URI: http://www.mywebsite/index.php

The line of code it refers to is:
<?php header('Content-type: text/html; charset=utf-8'); ?>

I am linking to this javascript file:
<script src="Scripts/AC_RunActiveContent.js" type="text/javascript"></script>

Any ideas on what could be causing this error?

Thanks