.thumbnail_off{
position: relative;
z-index: 0;
}

.thumbnail_off span{ /*CSS for enlarged image*/
position: absolute;
background-color: black;
padding: 5px;
left: -1000px;
border: 2px solid gray;
visibility: hidden;
color: black;
text-decoration: none;
}

.thumbnail_off span img{ /*CSS for enlarged image*/
border-width: 0;
padding: 2px;
}