This is a matter of considerable dispute. The following is an attempt to gather various viewpoints from the web into one place.
Web Design
From http://www.sun.com/950801/columns/MaryMorris.col9508.html : "So how can we tell a well-designed Web page from a poorly-designed one? Everyone has their own point of view: The Web is the elephant and we are the blind men, each of us coming from a different discipline, declaring the Web to be something else."