An activity diagram to describe the resolution of HTTP response status codes, given various headers.
The original repository sits at https://code.google.com/p/http-headers-status/ .
This repository is just a clone, plus a PNG export (via OmniGraffle).
This 2008 idea is being followed-up at https://github.com/for-GET/http-decision-diagram .