Interesting idea of creating a very thin shadow just after the modal elements of the browser window. From spyrestudious.com

gistfile1.css

body:before {
    content: "";
    position: fixed;
    top: -10px;
    left: 0;
    width: 100%;
    height: 10px;
    -webkit-box-shadow: 0px 0px 10px rgba(0,0,0,.8);
    -moz-box-shadow: 0px 0px 10px rgba(0,0,0,.8);
    box-shadow: 0px 0px 10px rgba(0,0,0,.8);
    z-index: 100;
}