The entries of the following list are in alphabetical order of the domain names. Please see the archive file if you would like to feel nostalgic by remembering lost ones.

https://aperiodical.com/math-404

http://math.arizona.edu/academics/math-404

• https://web.archive.org/web/20200825175755/https://www.math.arizona.edu/themes/uamath/img/404.png

https://www.magnt.com/math-404

• https://web.archive.org/web/20160115005749/http://magnt.com/404notfound/

https://mathigon.org/math-404

https://www.mathworks.com/math-404

• https://web.archive.org/web/20170105060053/https://www.mathworks.com/404.html

https://mc-stan.org/math-404

• https://web.archive.org/web/20171113121135/http://mc-stan.org:80/404.html

https://www.maths.nottingham.ac.uk/math-404

• https://web.archive.org/web/20131216155846/https://www.maths.nottingham.ac.uk/errors/findx.gif

https://math.stackexchange.com/math-404

• https://web.archive.org/web/20230824035932/http://cdn.sstatic.net/Sites/math/img/404.png

https://mathematica.stackexchange.com/math-404

• https://web.archive.org/web/20231205221416/http://cdn.sstatic.net/Sites/mathematica/img/404.png

https://stats.stackexchange.com/math-404

• https://web.archive.org/web/20160613103912/https://cdn.sstatic.net/Sites/stats/img/404.png