Recently, I’ve discovered that some of the Firefox version 2 (in particular 2.0.0.20 on Window Vista) has an error in the mime type settings. Reasons for this is because when I uploaded a PDF document (using cffile tag) via the Firefox browser the mime type returns from the browser was ‘text/html’ instead of ‘application/pdf’. Patrick van Bergen wrote a detailed article about this issue and has concluded that this occurs due to the incorrectly configured mimetype.rdf file located in the Firefox profile folder. There’s no common solution for this issue so far and the best we can do is to perform checks for both the mime type and the file extension to determine the content of the file.