body {
    background: #f0efe3;
}

#container {
    position: absolute;
    left: 50%;
    top: 10%;
    width: 1018px;
    height: 671px;
    margin-left: -509px;  /*set to a negative number 1/2 of your width*/
    margin-top: -67px;
    background-image: url('images/Cath_Rampton_web_page.png');
}