Make a new picture. 400px x 400px with a white background.
Make a new layer and call it gradient. Fill this layer with a dark color, I used #1A3240.
Now add a Layer mask, by pressing the layer mask button on the bottom of the layer panel.
Reset the colors by pressing D. Fill the layer with a gradient. it should look like the one we have below.
It's time to make the grid. Make a new picture (Ctrl+N). 4x4pixels and transparent. Use the pencil tool and draw two lines like in the image below. It's easier if you zoom in.
Now press Edit -> Define Pattern. Call it grid.
Lets go back to the main picture, here we make a new layer and call it grid. Press Edit -> Fill and select pattern from the roll out. Select the grid pattern and hit ok.
Make a new layer mask. And fill it with a gradient. A little longer in on the picture with this one. Move the grid layer below the gradient layer and you're finished.
Experiment with the effect to get the feel on it. Enjoy