Blank Screen When I Click The Test Play Button

Hey, I'm new to unity, like REALLY new. So I'm watching a tutorial on YouTube, following every step, and copying everything he does. In this tutorial he is showing you how to make a Main Menu for a multi-player game. I copy everything he does, but it comes to test playing the game, the screen just goes blank, here is an image

https://www.dropbox.com/s/wxv8gba3w7kitho/Untitled-2.jpg

So I went back to see if my camera was turned on, and that i had the correct layer selected, and position, and all that stuff, but everything was identical so I have NO idea what to do. Could someone please help me? Here is the tutorial

http://www.youtube.com/watch?v=o_wQ8Kw6A_s