Apply Add a Mask option for this layer (on the layers’ panel bottom) and choose the Gradient Tool (G) to dark out the lowest part of the background.

Now we shall use the Rounded Rectangle Tool (U) to represent the primary layer, reserved for the site’s sections, out of which we’ll cut out several circles (pressing the Alt button and using the Ellipse Tool (U)).

The layer’s parameters:
Blending Options>Outer Glow

Blending Options>Inner Glow

Blending Options>Gradient Overlay

Gradient’s parameters: