#spin {
    margin: auto;
    width: 100%;
    height: 100%;
    z-index: 1000;
    background-color: grey;
    opacity: .8;
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
}

.ajax-loader {
    position: absolute;
    left: 50%;
    top: 50%;
    margin-left: -32px; /* -1 * image width / 2 */
    margin-top: -32px; /* -1 * image height / 2 */
    display: block;
    opacity: 0.5;
}