.yellow-box {
    background: #ffc107;
    display: block;
    height: 150px;
    margin: 5px;
    padding: 20px;
    width: 25%;    
}
.black-box {
    background:black;
    color: white;
    display: block;
    height: 150px;
    margin: 5px;
    padding: 20px;
    width: 25%;
}