User-centered DesignUser-centered design is a process in which the needs, wants, and limitations of end users of a product, service or process are given the primary focus of attention at each stage of the design process.
The main difference from other product design philosophies is that user-centered design tries to optimize the product around how users can, want, or need to use the product, rather than forcing the users to change their behavior to accommodate the product (aka. Engineering-Centric Design).
See also: http://www.w3.org/WAI/redesign/ucd
Usability Testing