Shadow on upper-left.
box-shadow: -10px -10px orange;

Shadow on lower-right.
box-shadow: 10px 10px orange;

Blurred edges.
box-shadow: 10px 10px 20px orange;

Spread-out shadow.
box-shadow: 10px 10px 20px 10px orange;

Inset shadow.
box-shadow: 10px 10px 20px orange inset;