I had a similar issue with portrait/landscape mode in iOS 7 and this fixed it:
Check your html meta tags for something like this:
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, user-scalable=0">
Replace it with this:
<meta name="viewport" content="width=device-width, height=device-height, initial-scale=1.0, maximum-scale=1.0, target-densityDpi=device-dpi" />