Jon Yablonski has created a site that crisply illustrates the "Laws of UX" — some well-known precepts of how people interact with on-screen information.
One of my favorite laws, which you see in action all the time in the real world, is the "Serial Position Effect". As Yablonski describes it …
The serial position effect, a term coined by Herman Ebbinghaus, describes how the position of an item in a sequence affects recall accuracy. The two concepts involved, the primacy effect and the recency effect, explains how items presented at the beginning of a sequence and the end of a sequence are recalled with greater accuracy than items in the middle of a list. Manipulation of the serial position effect to create better user experiences is reflected in many popular designs by successful companies like Apple, Electronic Arts, and Nike.
(Via Sarah Drasner)