The error message you will probably never see
The most widely known error code for the everyday internet user is most certainly the 404 Not Found error response, which comes up when you type the wrong address or follow a broken link. Error 404 belongs to the 400’s family of error messages, all related to a client error, that is when something goes wrong on your side.
Another common message is the 403 Forbidden response, when you have no rights to see or access the content in question. But there is a rare case when the error code you see is 418. And this happens only when you try to control a coffee pot, and the server is in fact a tea pot.
This is not a joke, or, actually it IS a joke, but not from us. The I’m a teapot error message was defined as part of the Hyper Text Coffee Pot Control Protocol (HTCPCP), in an April Fool’s Day edition of the Internet Society’s Request for Comments publication on 1 April 1998. The protocol has a list of commands, such as the WHEN command that stops the server pouring milk into the coffee, and GET that retrieves coffee from the HTCPCP server.
So, if you happen to see the 418 I’m a teapot error message during your daily browsing session, it means you have tried to brew coffee with a teapot, so you need to search for a coffee pot instead.