.ad-banner {
    display: block;
    overflow: hidden !important;
    position: relative;
    margin: 10px 15px 5px 15px;
    text-align: -webkit-center;
    text-align: -moz-center;
    text-align: center;
    display: block !important;
    height: 250px !important;
    max-height: 250px !important;
}