That looks like it might be a Chrome or Firefox browser.
It seems like the Unity Plug-in didnt boot up when you clicked play. The Player, I've noticed, is a LARGE program and is only launched when you finally hit the "Play now" button to open the Web Player.
The only thing my still technologically inexperienced brain can suggest is to re-install the web player.
If that doesnt work, try running it on another Browser.