As GA was just breaking things, I was staring at the rather bare bones Bad Gateway error page and thought: we really need custom error pages. My favourite example is IMDb that uses movie quotes, but there are many others, and we could definitely make ours distinctly British. So I am opening the floor to suggestions - perhaps a slice of UK life ("popped down the shop for more beans", we may be able to get a maintenance page in, so something like road works) or some Carry On sauce ("Oo missus, the server has gone down on you, no extra charge") or Pythonesque or... something else. People won't see them often but it should, hopefully, get a smile when it does all go tits up (which sounds like something we could use).
Common errors:
400 - Bad Request
401 - Unauthorised
403 - Forbidden
404 - Not Found
500 - Internal Server Error
502 - Bad Gateway
Or if.you have a good idea for a rare one, or you have a personal favourite error code that's not being catered for, then ask and we can add it to the list.