html, body {
    width: 100%;
    height: 100%;
    margin: 0;
}

body.bg {
    background-image: url(../img/background.jpg);
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
}

div {
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-family: "Arial";
    font-size: 24px;
}