I've been mulling over different uses of HTML in crafting "documents", and I tripped over this quite by accident:http://techno-anthro...e-venn-diagrams.html
Scroll down a bit. You'll see a SELECT element used.
It's one thing that I'd never considered before, even though I commonly use the "A/B/C/D" structure. This simply does that in a different way with an HTML element.