For some reasons, Facebook doesn’t want to fix “Like it” box so that it will be easily integrated into your Facebook application page. So, there is a workaround, which allows you to place Like box for your application into your app page.
In this case I got a part of the iframed page http://www.facebook.com/connect/connect.php?id=127104720672096, there id – is your application’s id.
See, how it looks in my app https://apps.facebook.com/jbirthday