The problem is now fixed in iOS 7.0.3. But, if you can't go there, please read on.
This seems to be a defect in iOS7. To recap, the problem happens when you run a iPhone only app, compiled with iOS7 SDK, in a iOS7 iPad or iPad Mini. A temporary work around is to scale the scroll view of the web view. This makes the text look smaller than you will like, but, so far, this is the best solution I have seen.
- (void)webViewDidFinishLoad:(UIWebView *)webView {
CGSize contentSize = webView.scrollView.contentSize;
CGSize viewSize = self.view.bounds.size;
float scale = viewSize.width / contentSize.width;
if (scale < 0.9) {
NSLog(@"Zoom out fix for web view: %f", scale);
webView.scrollView.minimumZoomScale = scale;
webView.scrollView.maximumZoomScale = scale;
webView.scrollView.zoomScale = scale;
}
}