My phone show blank page after i start the App

hi,

i make an app for android using unity4 free version. i build and install it on my phone but when i try to start the app it just show a black blank page after the unity start up. Did i miss any step making a simple android apps?

All i make is just a background image with camera then i save it. build it . install it. but when i press the app on my phone it start up the unity logo and go blank.