.griglia {
width: 130px;
height: 130px;
float: left;
display: inline;
margin: 3px;
background-position: center center;
background-repeat: no-repeat;
}

.ombra {
width: 100%;
height: 100%;
filter:alpha(opacity=50);
opacity:0.5;
background-color: #CCCCCC;
float: left;
display: inline;
}
.ombra:hover {
filter:alpha(opacity=0);
 	opacity:0;
}