A computer science term, interface is the point of communication between the computer and any other entity. User Interface, or UI, narrows that definition down to the communication between the computer and a human being. Web designers have taken the sense of this communication of inputs and outputs as a useful way to describe how a user is informed by the design elements on a page. A “good” user interface can mean that the design fulfills a user’s expectations. A “bad” user interface gives you few clues about where you are or what you’re supposed to do, leaving you with the sensation that you’re drowning and don’t know which way is up. This condition is known as web vertigo.