#about_img {
    width:800px;
    height:480px;
}

/* ******** Mobile Stuff ******** */
@media (max-device-width: 720px), (max-width: 720px) {
    #about_img {
        width:100%;
        height:auto;
        max-width:800px;
        max-height:480px;
    }

}