I have a small mobile phone app that is acting strangely on the iPhone/Mobile Safari. The page renders and works great when it\'s orientation is vertical. When I rotate the phon
It's because Mobile Safari on iPhone & iPod Touch does automatic font-size adjustment.
You can disable it with the following css rule,
html {-webkit-text-size-adjust:none}
More info from Safari Reference Library
Have you tried including a viewport meta tag, such as this:
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no"/>
Otherwise, you could try creating orientation-specific CSS stylesheets and swap them out w/ javascript when the orientation change event fires, but I prefer the meta tag method above.