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

.thumbnail:hover{
background-color: transparent;
z-index: 1;
}

.thumbnail span{ /*CSS for enlarged image*/
position: absolute;

left: -1000px;
border:1px solid Gray;
visibility: hidden;
color: black;
text-decoration: none;
}

.thumbnail span img{ /*CSS for enlarged image*/
border-width: 0;
padding: 3px;
}

.thumbnail:hover span{ /*CSS for enlarged image on hover*/
visibility: visible;
top: 5px;
left: 10px; /*position where enlarged image should offset horizontally */

}