EllisLab/CodeIgniter — pull request #1016 by kevincupp (2012-02-05 19:17:09+00:00)
Title: Adding in a few 503 status codes for common errors

This is in response to an ExpressionEngine bug where reverse caching proxies would cache errors because they appeared to be normal 200 requests, so I've changed the status code to something more appropriate.

http://expressionengine.com/bug_tracker/bug/17420