When you download it, to play the game you have to run the index.html file. And the curse of spookiness was the version that came out in October and it has a bunch of Halloween related stuff.
"This version has some spooky scenery, candy from exploring and fighting, and enemies with cute costumes (the Angry Shark has 3 different costumes - you can try to get a peek at all of them!). There's a city-wide yard sale event going on. If you explore you might find a copy of a bootleg video game - try playing it, it's fun! Also, don't forget to stop by the Magic Shop to pick up your very own pet spider!"
Every October, all of these things will be available in the regular versions of the game as well.