The elements of user experience

Jesse James Garrett does an excellent job of illustrating the layer, the process, the essence of a user-centred design.

Print this off and put it on your wall. Reflect upon what happened when you last were involved in a website from scratch and which elements were overlooked. I have and I do.

Depressing and enlightening in equal measure.

The elements of user experience by Jesse James Garrett - PDF download

This was the foundation for Jesse's subsequent book:

The Elements of User Experience: User-Centered Design for the Web - book by Jesse James Garrett