I know how to use CSS3 shadows. However I am trying to achieve a specific design. I want the shadow to be a lot lighter and faded off on the left and right edges, please see image attached.

The only code I have come up with is the following. But not sure how to make the edges fade out more.
.shadow {box-shadow: 0 10px 6px -6px #000000;}
Any tips be helpful
I use a combination of box-shadow, border-radius and clip.
http://dabblet.com/gist/2225507