Open a new file, having 749×235 px and 72 dpi. Take the indicated tool and create the lowest background of the site’s header to be.

Blending Options-Gradient Overlay

Gradient’s parameters:

On a new layer of 4×4 px with this instrument must be inserted this picture:

then

keep the cliché
On a new layer with 749×235 px and 72 dpi must be applied next indications: