I'm a fan of these easter eggs. Especially when it fits with the theme of your site (apparently he's very into js). I started implementing a similar concept on my site awhile back... didn't quite finish, but any kings quest fans out there might get a kick out of my working concept:

http://www.robscanlon.com/kq/

"Sorry the princess doesn't put out. Let it go" - Really? (at the end of the level)

Up Up Down Down Left Right Left Right ABAB Start ... damn still no. Over 25 years of rescuing her from the jerks of the world. Getting tired of being in the friend zone.

Tacky message at the end totally ruined it. That is going to lose you sales.

Speak for yourself. I chuckled. It was immature, but man, there's so little time in the day to spend it getting worked up over a corny joke.

I'm totally not affiliated with that website. I actually found it by accident searching for some Javascript information

With a name like nihilogic, I don't think he cares.

Let me some A/B testing on that; the laugh by some of the visitors may actually increase sales. But this is speculation, just like yours.

An added easter egg: he stores mario's position in a cookie, so when you return to the site, mario is where you last left him: mario-data=2008%2C190%2C10

Really cool. Would love it if hitting the ? blocks actually did something cool ;) - great job.

It may be a stretch of the word 'playable', but pretty neat.

It's definitely playable; the stretch is calling it a game.

Amusing, but its use of the arrow keys breaks scrolling.

Like the endlessly falling Mario if you drop off the world in the crack. Goes off the bottom, re-appears on the top and falls through ad infinitum.

Woah, I thought it would be too distracting before I clicked through, but it actually wasn't. Great way to keep your site fun and original.

I still feel it's pretty distracting. It's a neat demo, but I wouldn't use it as a background on anything where I wanted someone to really focus on the actual content.

I disagree. This qualifies as an easter egg to me. I wouldn't have noticed the background if I came for the content. But a lot of traffic was gained by offering the feature... so net win?

That said, I came for the game, found it and still haven't read a single word on the page so... useless traffic I suppose.

But I wouldn't consider it distracting.

Wow, I used to chat on an IRC server that guy hosted on this domain. Small world.

A little bit ironic to sell a book about HTML5 games using IMG tags for the background game.

It's basically an easter egg, not a full blown demo of the author's skills..