[forgotmypw17]

I would add a basic feature-complete website which works on every mainstream browser starting with Mosaic.

It's much easier than it may seem, architecting it is interesting, and there is a lot of "last 10%" stuff which keeps it fun as long as you keep going.

In the demystifying area, it demystified HTML and JS history for me, forced me to use with a minimal toolkit, and taught me how to build "modern" JS features in ways which will not break browsers which don't know how to do them or have them disabled.