.center {
    margin: 0;
    position: fixed;
    top: 50%;
    left: 50%;
    bottom: 50%;
    height: 200px;
    width: 200px;
    right: 50%;
    margin-right: -50%;
    transform: translate(-50%, -50%);

    -webkit-animation: fadein 2s; /* Safari, Chrome and Opera > 12.1 */
       -moz-animation: fadein 2s; /* Firefox < 16 */
        -ms-animation: fadein 2s; /* Internet Explorer */
         -o-animation: fadein 2s; /* Opera < 12.1 */
            animation: fadein 2s;
}