The Unicorn of HTTP responses

Hyper Text error codes are generally unwelcome, but there is one error code that is pure magic and some day I hope to see it. That is error 418. Let me share the meaning of the elusive 418.

418 - I'm a teapot

   Any attempt to brew coffee with a teapot should result in the error
   code "418 I'm a teapot". The resulting entity body MAY be short and
   stout.

To understand when you might need that particular error code it helps to know about RFC 2324, which describes HTCPCP, a protocol for controlling, monitoring, and diagnosing coffee pots. So, if your coffee pot turns out to be a teapot you get a 418 and rightly so. Emacs (being somewhat of a unicorn itself) includes a full implementation of the protocol, and there are patches for firefox. Oh dear. I must be going. A rabbit in a waistcoat just ran by and dropped his pocket watch. I'd better return it.