Some smart phones and wireless PDAs display Web pages using the Wireless Application Protocol(wAP). WAP allows Web pages formatted in HTML to be displayed on devices with small screens, such as mobile phones. Another approach, made possibl by increased screen resolution, is to display a normal Web page on the device. The Apple iPhone was one of the first devices to include touch screen controls that make viewing and navigating a normal Web page easy to do on a small handheld device. A third approach is to design Web sites to match specific smart phones. This is much more difficult to accomplish because there can be many different phones that use the same operating system, and each phone has a different interface(the buttons, touches or gestures that perform specific functions often vary)