http://9rules.com/blog/2006/08/a-gradient-tutorial/If you add together all the “interface tricks” designers use on 1) websites, 2) blogs, and 3) web applications, the one common thread is the idea of manipulation. When we use gloss, gradients, or drop shadows it’s because we’re trying to manipulate your eye into thinking the 2D screen in front of you is a lush 3D landscape filled with volume, depth, and light sources. When you visit a site that looks really sleek and cool, it’s probably because they manipulated your eye correctly and the 3D effect looks “real”, and on sites that look odd or “not as real” it’s because the effects they used didn’t mimic what your eye believes as 3D. Your eyes have been looking at things in the world for a very long time and they’re used to what a shadow looks like, what a light source’s highlight on an object looks like, etc. If you don’t approximate what your eye “thinks” something should look like then your design won’t accomplish the 3D look you’re trying to emulate.
