@Albatros78, Molx is correct that the iPhone mobile safari does not hide the button bar by default unless it is launching a mobile webapp that has been saved to the home screen (i.e., Apple calls those WebClips). The Test Center provides a Strict Webclip Mode that is disabled by default. If you enable this mode then you will see very similar behavior as mobile safari re: the button bar’s appearance.
Summary: on iPhone you must save your webapp as a bookmark on the homescreen to avoid seeing the button bar when the app is launched.
Wayne
Genuitec Mobile Team