Last modified: 2008-02-05 00:07:50 UTC
A query like http://en.wikipedia.org/w/api.php?action=query&prop=revisions&meta=siteinfo&titles=Main%20Page&rvprop=user|comment&format=txt returns the following header: Content-Type: text/text; charset=utf-8 This isn't a common MIME type. Apparently query.php returned text/html; text/plain is an option as well.
This is deliberate for security purposes (to keep MSIE from being an XSS vector)