Just a few notes to record my thanks for various hints and tricks, bits of code, and sometimes actual one to one help.
Many thanks to Neocities for making this site not only possible but easy.
This site runs of Neocities so server side includes are not possible. I also want to edit the HTML directly so templates executed before upload are not all that convenient either. A solution is client side includes and Michael Marr (known as LexmarkWeb on GitHub wrote a tiny script to do just that.
Another convenience is that client side includes means that if I change one of the included files that is the only one that has to be uploaded.
I copied the minified script and added this to the head of my pages:
Then wherever I want another file included I just add a div like this: