div.cover {
    opacity: 0.2; /* for Firefox, Safari, and others */
    alpha(opacity = 20); /* for Internet Explorer */
    color: black;
    background-color: black;
    background-image: url(../images/youtube-play.jpg);
    background-position: center;
    background-repeat: no-repeat;
    z-index: 1;
    position: absolute;
}

div.teaser {
    z-index: 0;
}