Horizontal and vertical offset values of the box-shadow property specify the position of a shadow and can be both positive and negative.

• The horizontal offset — the x-axis value — can be positive, and the shadow will be on the right of the box. A negative offset value puts the shadow on the left of the box.
• The vertical offset — the y-axis value — can be positive, and the shadow will be below the box. A negative value sets the shadow above the box.