Unless it's been fixed in the 8 minutes since you posted, it does say 404 error in the graphic (in a thin font, though, so it's hard to see).

I agree that it should be in the page title, be more visible, and explain what "404 error" means, though.

I cannot see it. Might be an issue this side then. I see the asteroids floating around, and if I hit it I see a ship and can play an asteroids-like game.

It's just before you hit the space bar to begin playing the game, "404 Error! Press space to start," then it goes away. I missed it too until I saw your comment, then I went back and checked.