Forum Moderators: coopster
Or download the file, and see if you can modify the line creating the problem, it seems to me the file extensions are re-written to an extension type not-recognizable by the server.
A/ Download your .htaccess file using an FTP app
B/ Open it and look for some AddType statement (AddType)
The thing is that the extension your website is using is not recognize (html, htm, asp, php or anything else ?) and your server therefore is forcing the file to be downloaded.
Do a search for "Htaccess Mime type" or "AddType".
Tomda