I have recently (Jan 2022) moved this personal website from
sriar.github.io (hosted on Jekyll and Github Pages) to a pure html+css website inspired (read stolen) from vincentdoerig/latex-css. I had wanted to migrate out of Github Pages for a long time, but what finally pushed me over was that this theme had sidenotesHello there!, which are the closest to book footnotes that I can have on websites. Gwern has an article on various implementations of sidenotes on the interwebz if you would like to add sidenotes to your website as well.
I have tried (and tested) my hand at various things, at an average rate of once every two years.