The following Internet drafts and online documentation can give you more details about content negotiation:

http://www.ietf.org/rfc/rfc2616.txt

RFC 2616, "Hypertext Transfer Protocol-HTTP/1.1," is the official specification for HTTP/1.1, the current version of the HTTP protocol. The specification is a well-written, well-organized, detailed reference for HTTP, but it isn't ideal for readers who want to learn the underlying concepts and motivations of HTTP or the differences between theory and practice. We hope that this book fills in the underlying concepts, so you can make better use of the specification.

http://www.ietf.org/rfc/rfc2295.txt

RFC 2295, "Transparent Content Negotiation in HTTP," is a memo describing a transparent content-negotiation protocol on top of HTTP. The status of this memo remains experimental.

http://www.ietf.org/rfc/rfc2296.txt

RFC 2296, "HTTP Remote Variant Selection Algorithm-RVSA 1.0," is a memo describing an algorithm for the transparent selection of the "best" content for a particular HTTP request. The status of this memo remains experimental.

http://www.ietf.org/rfc/rfc2936.txt

RFC 2936, "HTTP MIME Type Handler Detection," is a memo describing an approach for determining the actual MIME type handlers that a browser supports. This approach can help if the Accept header is not specific enough.

http://www.imc.org/ietf-medfree/index.htm

This is a link to the Content Negotiation (CONNEG) Working Group, which looked into transparent content negotiation for HTTP, fax, and print. This group is now closed.

 

Hypertext Transfer Protocol (HTTP)