Monochrome image with CSS

monochrome-image.css

a.a-thumb {
    border: 1px solid black;
    position: relative;
}

a.a-thumb img {
    width: 60px;
    height: 60px;
    border: 0;
}

a.a-thumb span {
    background-color: #000000;
    position: absolute;
    top: 0;
    left: 0;
    width: 60px;
    height: 60px;
    z-index: 100;
    filter: alpha(opacity=20);
    -moz-opacity: 0.2;
    opacity: 0.2;
}

monochrome-image.html

<!-- HTML -->
<a class="a-thumb"><img src="/img/proxy-thumb.gif" /><span> </span></a>