Another website design query (Details...)

A company is considering me to build from scratch an entire site. I could really use the work. Amazing timing! Anyway, they were showing me a drop-down selector/match-maker – actually, I’m not even sure what to call it. Well, it’s here – basically the whole page is that drop down.

So, does anyone know anything about that style? What it’s called.? What programming language(s)? I’d really like to achieve that, but with my current skills, I’d have to use a template/pre-written code, or hire a programmer…

Bonus Points:
I’m probably going to use Squarespace for the layout since they make it pretty easy to do the heavy-lifting. Will that be a complication. I want to keep is as simple as possible