CSS Box Shadow

Used in casting shadows off block-level elements (like divs).

.shadow {
  -moz-box-shadow: 5px 5px 5px #ccc;
  -webkit-box-shadow: 5px 5px 5px #ccc;
  box-shadow: 5px 5px 5px #ccc;
}

1. The horizontal offset of the shadow, positive means the shadow will be on the right of the box, a negative offset will put the shadow on the left of the box.
2. The vertical offset of the shadow, a negative one means the box-shadow will be above the box, a positive one means the shadow will be below the box.
3. The blur radius, if set to 0 the shadow will be sharp, the higher the number, the more blurred it will be.
4. Color

Inner Shadow

Example
Internet Explorer Box Shadow
You need extra elements...

<div class="shadow1">
        <div class="content">
                Box-shadowed element
        </div>
</div>

.shadow1 {
        margin: 40px;
        background-color: rgb(68,68,68); /* Needed for IEs */

        -moz-box-shadow: 5px 5px 5px rgba(68,68,68,0.6);
        -webkit-box-shadow: 5px 5px 5px rgba(68,68,68,0.6);
        box-shadow: 5px 5px 5px rgba(68,68,68,0.6);

        filter: progid:DXImageTransform.Microsoft.Blur(PixelRadius=3,MakeShadow=true,ShadowOpacity=0.30);
        -ms-filter: "progid:DXImageTransform.Microsoft.Blur(PixelRadius=3,MakeShadow=true,ShadowOpacity=0.30)";
        zoom: 1;
}
.shadow1 .content {
        position: relative; /* This protects the inner element from being blurred */
        padding: 100px;
        background-color: #DDD;
}