Interfaces excel at one thing: enabling users to perform tasks without needing to understand the behind-the-scenes complexities. Flip a light switch, and you have light – without any electrical engineering expertise. The promise of simplicity and utility…that’s a good interface.

Interface disasters occur when that promise is broken.  For example:

• Isn't it quirky that we have to open the "Start" menu to shut down our computer session? Or press “End” to turn the cell phone on?
• Ever ponder the murky differences between "OK", "Apply" and "Cancel" buttons?
• It seems we have to sift through too many nested dialog windows just to find a few basic tasks, like changing the desktop background.
• Core interfaces, like volume controls, have been buried in odd places like the Windows® taskbar tray.
• Deciphering clusters of cryptic icons for abstract concepts (like "publish" or "indent bullets") where simple text labels would work better.

People have high expectations when using software or visiting a website. The Web 2.0 revolution has brought many innovations, like simplified graphics, contextual inline controls, direct-data manipulation (e.g. paging through photos on an iPhone) and global undo, all of which continue to be refined via web analytics and represent the future of human-machine interaction. So when designing an interface, use some common sense with icons and controls and basically stay out of the way of the user and their goals.