A Salon article inspired many examples from readers: https://www.gnu.org/fun/jokes/error-haiku.en.html

(I could swear that one of these appeared in BeOS' NetPositive browser if you visited a site without network access... but now I'm not so sure.)

Edit: now I'm sure: https://8325.org/haiku/

I find this one hilarious, and rather relevant to this thread:

"Errors have occurred.

We won't tell you where or why.

Lazy programmers."

Thank you for sharing them :)

That isn't a valid haiku, and it's much less clear, in my opinion. If you give me a nice big "404 Not Found" up front and then include a poem, HTTP cat, or easter egg, that would give the page personality while still being immediately useful.

Of course, it is still both a 404 HTTP response and a proper HTML webpage - so both the user agent and the website have an opportunity to explain the error. If both of them try to be funny, though, that's no good.