They are still available on Chris’s website: http://chrishood.me/archive-unit-converters.php.
This was the first set of unit converters Chris built. There is a webpage for each type of unit and all calculations are done on the browser using Javascript, so the server doesn’t do any of the work. They were built in 2000 and 2001 and haven’t been worked on since. If you go to the archive page where they are right now, you can see one thing that doesn’t show up right in modern browsers. Amazingly some other code on the pages still works, despite having been deprecated.