<div id="postthumb">
<div id="postthumbimg">
<a href="#"><img src="http://www.fliparegalos.com/image/cache/data/235201213581465584d-168x168.jpg" /></a>
</div>
<div id="overlay"></div>
</div>#postthumb {
width: 282px;
height: 152px;
}
#postthumb #overlay {
opacity: 0;
position: absolute;
top: 0;
left: 0;
width: 282px;
height: 152px;
text-align: center;
}
#postthumb #overlay:hover {
position: absolute;
opacity: .7;
background: url(http://us.cdn4.123rf.com/168nwm/triken/triken1307/triken130700025/20761438-vector-realista-con-lupa-sombra-sobre-fondo-gris.jpg) no-repeat;
transition: opacity 150ms ease-in-out 0s;
width: 282px;
height: 152px;
}
