Silverlight-based browsers may request permission to stay in full-screen mode.
If you select Yes, Silverlight will stay in full-screen mode even if you switch to another application.* Whether you have multiple monitors or use a keyboard command to switch applications, Silverlight will remain the same. In this state you must manually exit full-screen mode.
If you select No, switching to another application will exit full-screen mode automatically.
If you check "Remember my answer," your response will be remembered and you will no longer be shown this dialog. Instructions on resetting this preference can be found here.
* Safari users, note that selecting Yes causes full-screen video to appear behind the web browser. Select No or reset your preference to avoid this behavior.