Use something like this
Which uses something like:
.knockout-top-to-bottom {
position: relative;
}
.knockout-top-to-bottom:before, .knockout-top-to-bottom:after {
content: "";
position: absolute;
}
.knockout-top-to-bottom:before {
top: -3px;
left: -3px;
bottom: 0;
right: -3px;
background-image: -webkit-gradient(linear, 0 0, 0 100%, from(#000), to(transparent));
background-image: -webkit-linear-gradient(#000, transparent);
background-image: -moz-linear-gradient(#000, transparent);
background-image: -o-linear-gradient(#000, transparent);
z-index: -2;
}
.knockout-top-to-bottom:after {
z-index: -1;
top: 0;
left: 0;
bottom: 0;
right: 0;
background: #a4b9ff;
}
solved How can I make an effect of fading shadow with css3?