body {
    font-family: "Source Sans Pro","Helvetica Neue",Helvetica,Arial,sans-serif;
    background-color: #2196F3;
    color: #337ab7;
}

.center {
    position: absolute;
    width: 100px;
    height: 50px;
    top: 50%;
    left: 50%;
    margin-left: -50px; /* margin is -0.5 * dimension */
    margin-top: -25px; 
}