@atbk
A few questions to give me a better idea of what might be happening:
1) what version of mobione are you using? See Help>About for the version info.
2) on which devices does the white area appear?
2a) if on iOS device does the white area appear only when the webapp is launched from the home screen or does it appear all the time such as when loaded from the web?
3) can you send me one of your design files that is having this problem for investigation? Send to support at genuitec dot com with the MobiOne in the title.