One of my favourite 404 pages was this:
http://www.homestarrunner.com/systemisdown.html
Edit: Corrected the 50X error information thanks to the responses below.
It would not be correct for a request for a page named "error" to return 404 Not Found if the page named "error" was retrieved successfully.
It would also not be correct for a request for a page that does not exist to return the page named "error" with a 200 OK status.
2) I made an assumption, based on the context, that this page was serving a role that is used when the server is overloaded or otherwise unavailable. In that case, this page should not be serving a 200 status, it should be serving a 50X response.
Now, it's possible that this page is just a demonstration of the error that would normally be produced when the website is unavailable. In that case, sure, 200 status is proper since it's not meant to actually be the literal error page which is served when the site has gone down. It's also possible the page has logic in it to serve 200 error when requested directly and 50X when the server is down.
In really, I bet this page is served as-is when the website is unavailable and sends a 200 error. It's difficult to know whether or not this is true until we see a real problem with the server.
It's a fun page but horribly executed. The customer has no idea what's actually happening. Is this a server problem or is the page actually missing?
503 (Unavailable) is more suitable for that I guess.
Wow. I guess the income from the swag (and their 15 minutes) ran out.