It's a form of binary code.
Every third "character" consists of all four lights switching on (three on top, one below). Think of that as a separator character. For the other characters, the bottom light is always off, so ignore it and read the top 3 as binary:
3 4 _ 1 6 _ 5 1 _ 5 0 _ 3 2 _ 0 7
We can read that as 34 16 51 50 32 07. If you reload the page and only flip over the cards with those numbers, you will be redirected immediately to the FlynnLives Discussion Forum.
I can't take credit for discovering this, so don't be too impressed.
-- Histrion