New skins or a universal skin should be created.
Now there is only one iPhone 3 skin which is used to render all devices, including iPad, Android and BlackBerry. But there are differences between these devices, which should be reflected skins. For example, iPad has back/forward buttons on the address bar and the address bar is never hidden. Android, in its turn, has back/forward buttons either as hardware buttons (not on screen), or they are hidden automatically. For developers this means, that available browser size differs from iPhone 3.