Edit in JSFiddle

<div class="stage">
    <div class="cube">
        <div class="front"></div>
        <div class="back"></div>
    </div>
</div>
div.stage{
    position: relative;
    top: 100px;
    -webkit-perspective: 500;
    div.cube{
        width: 200px;
        height: 200px;
        position: relative;
        margin: 0 auto;
        div{
            width: 200px;
            height: 200px;
            border: 1px solid #999;
            box-sizing: border-box;
            text-align: center;
            line-height: 198px;
            position: absolute;
            background-color: rgba(255,255,255,.7);
        }
        div.front{
            top: 0;
            left: 0;
            -webkit-transform: translateZ(100px);
        }
        div.back{
            top: 0;
            left: 0;
            -webkit-transform: translateZ(-100px);
        }
    }
}