.vimeo_div_thumb {
    position: relative;
    min-height: 320px;
    height: 100%;
}

.vimeo_div_thumb iframe {
    width: 100%;
    position: absolute;
    height: 100%;
    left: 0;
    bottom: 0;
    background: #fff;
    /*border: 2px solid #000;*/
}