[css] CSS Box Shadow Bottom Only

try this to get the box-shadow under your full control.

    <html>

    <head>
        <style> 
            div {
                width:300px;
                height:100px;
                background-color:yellow;
                box-shadow: 0 10px black inset,0 -10px red inset, -10px 0 blue inset, 10px 0 green inset;
           }
        </style>
    </head>
    <body>
        <div>
        </div>
    </body>

    </html>

this would apply to outer box-shadow as well.