Click the link and play the little game. Using the scroll keys or you mouse wheel might work faster and better than clicking so try what works best for you. You will have to use clicking at least three times though (you will work out where)
If you do it right, you can get three Steam keys, namely for:
A bird story: 84% positive: http://store.steampowered.com/app/327410/ plus trading cards
Cloud Knights: 65% positive: http://store.steampowered.com/app/360130/
Defend your life: 85% positive: http://store.steampowered.com/app/357780/ plus trading cards
No spoilers in the comments please. If you cannot figure it out by yourself, you really do not deserve the three free Steam keys.
Enjoy.
Note: When I used IE the frame rate for the game was terrible. When I used Firefox it was fluid, normal and fine. Not sure if it will be the same for you but worth a try.
nice thanks