/* CSS Document */
.mainDiv {
    width: 100px;
    height: 100px;
    position: absolute;
    top: 50%;
    left: 50%;
    margin-left: -50px;
    margin-top: -50px;
}

div.centered {
    position: absolute;
    top: 15%;
    left: 25%;
    width: 50%;
    height: 50%;
}

body {
    height: 100%;
    padding: 0;
    margin: 0;
}