RFC1521 and RFC1522 specify the types and subtypes for Multipurpose Internet Mail Extensions (MIME). See also http://ds.internic.net/rfc/rfc1521.txt, http://ds.internic.net/rfc/rfc1522.txt, and ftp://ftp.isi.edu/in-notes/iana/assignments/media-types/.
The x- prefix for the content-type indicates that the extension is not considered a standard type and may change or be defined otherwise by other users.
A Web client uses these MIME types to interpret data retrieved
from Web servers. Users can find a database listing the connection
between the MIME type and file name extensions.
| Netscape | File name is listed in the Helper Applications section of the Preferences menu |
| Mosaic for X | mime.types |
| WinMosaic | MOSAIC.INI |
| MacWeb | Part of the program resource fork available from the pull-down menu |