Apple spend quite some time when designing basic user interface elements. The iPhone tab bar is certainly one of the most used one in iOS apps. But, as developers, do we always understand its real usage? Besides documented HIG from Apple, is there any rules that we should keep in mind when implementing UITabbar in our apps? You bet. If you have something that you have to do today, is read this excellent post from Petter Silfver @ Significantpixels: The iPhone Tab bar. Do it now.