It's generated using http://jashkenas.github.io/docco/. I think it's possible to use comments, but often it's "literate" source code, e.g. markup & code blocks.
Soundslice is a service where you can transcribe music easily. Many sites that offer "guitar tabs" use either an ASCII-based format or files for GuitarPro and similar programs. Soundslice allows you to transcribe directly from a YouTube video, so you get the original sound together with the tabs, looping, slowing down and the ability to transcribe songs yourself.
There is also a Google Chrome/Chromium extension also provided by the pdf.js team. (It's not in the webstore, though.)
I've used it since about half a year and I like it a lot. (Not having to download PDFs all the time and having PDFs in tabs alongside the sites I read.)