(If you decide to use an add-on and you need help with it, you should visit the add-on site or contact the add-on developer directly for support.) (To learn more, see Properly configuring server MIME types at MDN web docs.) You can contact the website in such cases or you can try a Firefox add-on such as Content-Type Fixer to work around the problem. For example, Firefox may display the content as plain text instead of opening the file in an application or asking you what to do. Note: Firefox will not be able to properly handle a file download if a misconfigured web server sends it with an incorrect Content type.