archive.org

Archive of Math 404

Internet Archive does a great job for preserving epic “404 Not Found” pages.

http://www.arbitraryconstant.co.uk/404.html

https://web.archive.org/web/20040610014501/http://www.arbitraryconstant.co.uk/404.html

Department of Mathematics, University of Connecticut

https://web.archive.org/web/20171108000513/http://www.math.uconn.edu/errorpage