body {
    font-family: sans-serif;
}

#box {
    position: absolute;
    top: 20px;
    left: 20px;
    width: 300px;
    height: 300px;
    background: #333;
    text-align: center;
    line-height: 300px;
    color: #fff;
    border-radius: 5px;
}