Edit:
Set _scrollview frame size and _childview frame size same:
//Frame for scrollview 56, 92, 196, 408.
_scrollView.delegate = self;
_scrollView.minimumZoomScale = 1.0;
_scrollView.maximumZoomScale = 10;
_childView=[[UIView alloc] initWithFrame:CGRectMake(0, 0, 196, 408)];
_childView.backgroundColor=[UIColor blackColor];
[_scrollView addSubview:_childView];
[_scrollView setContentSize:_childView.frame.size];
and implement this delegate
- (UIView*)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
return _childView;
}
Also check your auto resizing flag in XIB. it is set to bottom margin.