Usually the whole 3xx series of return codes, also any 2xx that isn't 200 and 204. If I find someone's "quick and dirty HTTP client library", I generally lose

Usually the whole 3xx series of return codes, also any 2xx that isn't 200 and 204. If I find someone's "quick and dirty HTTP client library", I generally lose hope that redirects are handled. Anything more complex than that (and there's a lot!) is pipe dream.