Let me add the following problem-fields of mimetypes being a source for confusion (esp. for file uploads): openacs has its own cr_mimetypes, there are different sources for standardizing extensions/mimetypes (e.g. IANA, apache config), furthermore different browsers get for different operating system different mimetypes when uploading files, which is a moving target. the whole issue is messy, but i guess there is room for improvement in openacs.
