Many of the protocols that control activity on the Internet are defined in Request for Comment (RFC) documents that are created, updated, and maintained by the Internet Engineering Task Force (IETF), the protocol engineering and development arm of the Internet. There are several important RFCs that you will find useful when writing Internet applications:

• RFC822, "Standard for the format of ARPA Internet text messages," describes the structure and content of message headers.
• RFC1521, "MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies," describes the method used to encapsulate and transport multipart and multiformat messages.
• RFC1945, "Hypertext Transfer Protocol—HTTP/1.0," describes a transfer mechanism used to distribute collaborative hypermedia documents.

The IETF maintains a library of the RFCs on their Web site, www.ietf.cnri.reston.va.us 

These documents include, among other information, details about

• Parts of a Uniform Resource Locator
• HTTP request header information
• HTTP server activity