Note that using the generic application/octet-stream MIME type for information you want the browser to simply save and not render won't always work under some (all?) versions of Internet Explorer. IE has a tendency of taking the MIME type with a grain of salt and doing further examination of the file's extension to determine whether or not IE should attempt to render the content internally. MS Office files (e.g. .doc) are notoriously difficult to bring up a "Save As" dialog, because some versions of IE insist on rendering it in an embedded MS Word window.