In FF it works like intended (puts light transparent ribbon on the bottom of the image for caption). But in IE it's totally black (caption does show)

.caption {
    z-index:30;
    position:absolute;
    bottom:-35px;
    left:0;
    height:30px;
    padding:5px 20px 0 20px;
    background:#000;
    background:rgba(0,0,0,.5);  
    width:300px;
    font-size:1.0em;
    line-height:1.33;
    color:#fff;
    border-top:1px solid #000;
    text-shadow:none;
}