sombra interna do CSS
/* offset-x | offset-y | blur-radius | color | inside */
box-shadow: 0px 1px 3px gray inset;
Rudolph Steyn
/* offset-x | offset-y | blur-radius | color | inside */
box-shadow: 0px 1px 3px gray inset;
div {
box-shadow: inset 0 0 10px #000000;
}
.box-bottom-shadow {
-webkit-box-shadow: 0 8px 6px -6px black;
-moz-box-shadow: 0 8px 6px -6px black;
box-shadow: 0 8px 6px -6px black;
}