It is a known fact that IE attempts to sniff out the mime type of files as they are downloaded. That is, IE checks the extension of the file, the content type, etc to try to determine if there is an application on the client PC that has been configured as the default for that type of file. So, when downloading a file with a .txt extension, it would offer to open the file with Notepad, or Excel if the file had a .csv extension. This is fine most of the time. But, occasionally, developers may want ......