In this tutorial I'll show you how to create, in very few steps, a nice and attractive header.
I have used this technique in a website I just developed and the outcome is really nice.
I think it's better if you use this tutorial to create a header where you'll have some ads displayed, as background for banners or text ad boxes.
Let's start creating a new document, I'll use a 500 px by 200px document.
Now pick the Rounded Rectangle with a 8px radius ( my example is 8pc, obviously you should use a radius that better fits your design ) and select #292929 ( dark grey, almost black ) as foreground color.
Draw the big rounded rectangle that defines the area of your header: here's mine.

Now create a new Layer, pick the Ellipse Tool, set white as foregroung color and draw some random small ellipses all over the rectangle: here's what I have now.

Now select Filter > Blur > Gaussian Blur and set it to 4 pixels.

The result should look like this:

Now go to Filter > Pixelate > Mosaic and set it to 10 Pixels

and you should get something similar to mine:

Now set this layer's opacity to 30% and go to Filter > Sharpen > Sharpen, and do it again twice (you can use CTRL+F).
Here's your squared header.