.hout{
    background-image: url("../images/hout-ringen.jpg");
  }

.card-img-top.grey {
    -webkit-filter: grayscale(100%); /* Safari 6.0 - 9.0 */
    filter: grayscale(100%);
}

.footer {
    font-size: 80%;
    text-align: right;
}