body {
    margin: 0;
    padding: 0;
}
#source-code {
    text-align: center;
    background-color: gainsboro;
    height: 40px;
    line-height: 40px;
}
/* -----*/
#content {
    padding-top: 2em;
    width: 400px;
    margin: 0 auto;
    height: 200px;
}