This site helped me: https://gist.github.com/ocean90/1268328 (Note that on that site the left and right are reversed as of the date of this post... but they work as expected). They are corrected in the code below.
<!DOCTYPE html>
<html>
<head>
<title>Box Shadow</title>
<style>
.box {
height: 150px;
width: 300px;
margin: 20px;
border: 1px solid #ccc;
}
.top {
box-shadow: 0 -5px 5px -5px #333;
}
.right {
box-shadow: 5px 0 5px -5px #333;
}
.bottom {
box-shadow: 0 5px 5px -5px #333;
}
.left {
box-shadow: -5px 0 5px -5px #333;
}
.all {
box-shadow: 0 0 5px #333;
}
</style>
</head>
<body>
<div class="box top"></div>
<div class="box right"></div>
<div class="box bottom"></div>
<div class="box left"></div>
<div class="box all"></div>
</body>
</html>