Gradients

Web 2.0 design has more gradients than the Alps.

Why gradients are so useful

Gradients soften areas that would otherwise be flat colour/tone.

They can create the illusion of a non-flat surface, used to good effect on Alex Dukal's portfolio.

Gradients can be used to fade a colour into a lighter or darker tone, which can help create mood.

In page backgrounds, they may also create an illusion of distance.

A common gradient combo is blue-to-white, which evokes the effect of aerial perspective, creating the sense that the background fades away towards the horizon.

They are commonly used at the very top of page backgrounds, where they help denote the boundary of the viewable area.

They're also an integral part of drop-shadows, and the inner-glows and specular highlights you see on glass- or plastic-style buttons.

Note that gradients usually work best when juxtaposed with areas of flat colour or tone.