Where can I find the list of httpd error codes that Tomcat can produce?

Alessandro A. Garbagnati

You can get a list of all the possible Httpd Status Code (error and not) can be found by reading the official RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1 from the W3 Consortium

The relevant part from that document is Chapter 10, from page 57 to page 71 included.