HTML files in folders

I would like to use CKFinder to upload and manage HTML files. I have it working with PDFs, and MS Word docs, but HTML files do not appear when browsing. I have set the $config as below. Any ideas as to why it will let me see 'pdf' files but not 'html' files?

$config['ResourceType'][] = Array(
'name' => 'Files',
'url' => $baseUrl . 'files',
'directory' => $baseDir . 'files',
'maxSize' => 0,
'allowedExtensions' => 'csv,doc,gif,html,jpeg,jpg,js,pdf,png,ppt,swf,txt,xls,xml',
'deniedExtensions' => '');

- Steve