.gallery {
    background: black;
}

.gallery-cell {
    position: relative;
    height: 550px;
    margin-right: 5px;
    width: 300px;
    -webkit-filter: grayscale(90%);
    /* Safari 6.0 - 9.0 */
    filter: grayscale(90%);
    counter-increment: gallery-cell;

    background-size: cover;
    background-repeat: no-repeat;
}

.gallery-cell .highslide-gallery>a {
    position: absolute;
    left: 0;
    right: 0;
    top: 0;
    bottom: 0;
}