Apple relies on each app developer to implement components in their apps that allow VoiceOver to work correctly. If an app you're using doesn't support VoiceOver, check the App Store for updates, or contact the developer of that app. To locate a developer's support website, navigate to the App Store and search for the app. The developer's website is listed on the app's product information page.
If an app doesn't provide full VoiceOver support, VoiceOver might skip over buttons or text areas, or it not speak the correct label for an item. To help with this issue, Apple introduced Custom Labels in iOS 5. With VoiceOver enabled, use a two-finger double-tap-and-hold gesture to open the element labeler. Then you can create your own labels for items in an app that are not labeled correctly.