I remember talking online to a musician friend of mine a while back about the sound of a certain music album. To be more specific, we discussed how the bass guitar sounds and how it is more felt than heard. Think about that. You can’t really make out the sound of an instrument, but you can feel it and it adds to the sound and the atmosphere.
The same applies to web design. A subtle graphical element, for instance, can make the world of difference. It can be a shadow, a gradient, or a glow you can’t even spot right away, but it can make the difference between unremarkable and remarkable.