body {
    padding-top: 56px;
    background: url('images/bg-sm4.jpg');
    background-attachment: fixed;
     background-size: cover;
     background-position: center;
   }

   * {box-sizing:border-box}

.thumb img {
    -webkit-filter: grayscale(0);
    filter: none;
    border-radius: 5px;
    background-color: #fff;
    border: 1px solid #ddd;
    padding: 5px;
}

.thumb img:hover {
    -webkit-filter: grayscale(1);
    filter: grayscale(1);
}

.thumb {
    padding: 5px;
}