Notes:

Player.IO is a service for building multiplayer Games and more. The site is built using HTML5 elements. I would suggest looking at the sectioning. For example under the “What can I use it for?” heading I would split each of those div’s into section’s as they each have a logical hierachy.

Another addition would be to change the input type to type="search" for the site search. It will degrade gracefully in browsers that don’t understand it.