style.css

*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}
body{
    background: #ccc;
}
section{
    margin-top: 100px;
}
.container{
    padding: 0px 10%;
}
.Box{
    position: relative;
    width: 100%;
    height: 300px;
    background: #fff;
    text-align: center;
    line-height: 300px;
    font-size: 60px;
}

.Box::after{
    content: '';
    position: absolute;
    right: 20px;
    bottom: 15px;
    background:#777;
    width: 50%;
    height: 20px;
    box-shadow: 0px 15px 10px #777;
    z-index: -1;
    transform: rotate(3deg);
}


.Box::before{
    content: '';
    position: absolute;
    left: 20px;
    bottom: 15px;
    background:#777;
    width: 50%;
    height: 20px;
    box-shadow: 0px 15px 10px #777;
    z-index: -1;
    transform: rotate(-3deg);
}