root 
{ 
    display: block;
}

.divContenitoreHide {
    position: absolute;
    display: none;
    background-color: white;
    }

.divContenitoreShow {
    position: absolute;
    display: inline;
    background-color: white;
    z-index: 1;
    }

.divOpacoShow{
    background:#aaa;
    position: absolute;
    display: inline;
    z-index: 2;
    filter:alpha(opacity=50);
    -moz-opacity: 0.5;
    opacity: 0.5;
}