Web design can be actually considered a form of art under many aspects. A web designer is a skilled designer with a strong background either in web standards or in graphical design. Many layout I've seen so far on the web are more than beautiful: they actually communicate some kind of inner poetry, a magic that moves from the screen and reaches the visitor's mind conveying the concept behind a web site or web project.
How can a user receive this message? How can sight convey such a concept? The idea behind all successful designs is that the user is a part of the design, and not only a mere spectator. Colors, graphics, gradients, typography work fine when a designer is able to include a casual visitor into his/her design by predicting how certain graphic combinations can affect the user's mind. It's more like painting a canvas than creating a PSD file. For example, the Gioconda's smile attracts the visitor with a subtle use of lights and shadows that gives you the impression of a living person who follows your curious eyes.
It's a smart effect, because the great Leonardo knew very well how the laws of distance and proximity do interact with our feelings. A masterpiece in web design occurs when both the designer and the user are in the same design or, in other words, when a user and a designer can exchange their roles in the inner working of site interactions.