.photo-gallery ul {
    margin: 0;
    padding: 0;
    list-style: none;
    overflow: hidden;
}
.photo-gallery ul li {
    float: left;
}
.photo-gallery-preview {
    position: relative;
    width: 100%;
    max-width: 600px;
}
.photo-gallery-preview img {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    max-width: 600px;
    height: auto;
    display: block;
}
.photo-gallery-preview img.current {
    position: static;
}