Problems with building compelling mobile services

1) Building mobile websites and services is challenging due to the wide diversity of mobile handsets that vary in features such as screen size, browser support, and input methods. 2) Common strategies for addressing handset diversity include targeting the lowest common denominator, conditional markup that renders differently based on device capabilities, and databases of device capabilities. 3) User identification is difficult on mobile due to unreliable cookie support and lack of consistent identifiers across carriers and devices.