It seems that there is a problem with the screen sizes for several (if not all - not verified) games on ArmorGames. Several users have made a thread about this problem, so it is best to redirect them all here into one main thread to keep a solid overview of the problem.
The problem has been forwarded to the staff and they will attend to it as soon as possible, but seeing as it is the weekend right now, it might take some time to get fixed, so please be patient with this matter... =)