I like this.

A List Apart: Articles: Understanding Web Design:

Web design is the creation of digital environments that facilitate and encourage human activity; reflect or adapt to individual voices and content; and change gracefully over time while always retaining their identity.

Let’s repeat that, with emphasis:

Web design is the creation of digital environments that facilitate and encourage human activity; reflect or adapt to individual voices and content; and change gracefully over time while always retaining their identity.