Usability

Studies of user behavior on the Web find a low tolerance for difficult designs or slow sites. People don't want to wait. And they don't want to learn how to use a home page. There's no such thing as a training class or a manual for a Web site. People have to be able to grasp the functioning of the site immediately after scanning the home page—for a few seconds at most.

Source: http://www.informationweek.com/773/web.htm;jsessionid=JZLCZAP35FFI3QE1GHPSKH4ATMY32JVN