Valid HTML?

Extract of a message from a friend:

I'm curious about this site .....

http://bw.org/

I look at the code, and it doesn't look like valid HTML,
actually, I don't know why it even works.

BTW, I wasn't being critical of his code, (I probably
should be), I just don't see how it works.

I am also curious -- all comments welcome.

James Pickering