It turns out that Netscape server's default mime type is "text/plain", and the .doc file extension isn't specifically listed as an exception. Because of this, Netscape's browser invokes the standard handler for type "text/plain", which is to translate what it sees as unix-style end-of-line characters to the local pla" files as "application/ms-word", if you want your clients to automatically run Word with this document. There is a separate mime.types file for each Netscape running on an individual port.
It might be worthwhile to add ".xls", ".ppt", and other frequently used extensions as type "application/octet-stream" if you think that your users might be sharing files of these types.