Lots of borders

Modal!

div.modal{
    width:400px;
    height:700px;
    background: rgba(255,255,255,0.2);
    margin:100px auto;
    border-radius:10px;
    border:1px solid rgba(255,255,255,.4);
    position:relative;
}

div.modal:after{
    background:rgba(255,255,255,.6);
    display:block;
    width:370px;
    height:670px;
    content:'';
    position:absolute;
    top:13px;
    left:13px;
    border:3px solid white;
    border-radius:3px;
}
div.modal:before{
    display:block;
    content:'';
    width:369px;
    height:669px;
    position:absolute;
    top:15px;
    left:15px;
    z-index:9999;
    box-shadow:inset 0 0 10px #000000;
}