The error appears when a page is trying to redirect to another but there has already been content outputted to the current page, for example:
<html>
<?php
/* This will give an error. Note the output
* above, which is before the header() call */
header('Location: http://www.example.com/');
exit;
?>
The “html” tag has already been output so the page will error when trying to redirect. Check if this is happening at all in your code
