Teens often work on laptops with track pads, making interactions that require precision — such as drop-down menus, drag-n-drop, and small buttons — difficult. Design elements such as rollover effects and small click zones are also problematic, if they’re usable at all. Small text sizes and dense text make reading difficult. Combine these elements with poor ergonomics and you have a prescription for fatigue and errors. –Jakob Nielsen

Teenage Usability (Jakob Nielsen’s Alertbox).