body {
    background-image: url("paper-texture.jpg");
    background-color: #cccccc;
   }

center {
    display: block;
    margin-left: auto;
    margin-right: auto;
    width: 50%
}

div {
    background-color: antiquewhite;
    max-width: 45%;
    margin-left: auto;
    margin-right: auto;
}

div.a {
    text-align: center;
}