OK,the script is supossed to find and fix any BOM marked file.
BTW I've checked
www.chantillyexpat.com with teh w3c validator and theres a BOM marked file on your site.
validator.w3.org/check...ator%2F1.2
If this happening using the default theme then is possible that the BOM marked file (hoping is just 1) is a PHP one.
As InspectorClueNo Said check for the common files, my first candidate is /includes/meta.php
If you're using the Geany editor to edit your files is so easy to tell if the BOM mark is present on a file. But weird, since the script is supossed to detect and fix those marked files.
Is it happening on ALL versions of IE9?
BTW, tested that script and failed to detect and fix a file on my site, to fix the problem go to line 20 on the cBOM.php file and find:
define('BOM', '');
And replace it to:
define('BOM', b"\xEF\xBB\xBF");
It at least detect NOW the BOM marked files but is not fixing the files and also solves the warning at line 57.