.thumbnail
{
    position: relative;
    z-index: 0;
}
.thumbnail:hover
{
    background-color: transparent;
    z-index: 50;
}
.thumbnail span
{ /*CSS for enlarged image*/
    position: absolute;
    background-color: #676767;
    padding: 0px;
    left: -1000px;
    top: -1000px;
    border: 0px dashed gray;
    visibility: hidden;
    color: black;
    text-decoration: none;
    width: 560px;
    height: 490px;
}
.thumbnail span img
{ /*CSS for enlarged image*/
    border-width: 0;
    padding: 0px;
}
.thumbnail:hover span
{ /*CSS for enlarged image on hover*/
    visibility: visible;
    top: -245px;
    left: -360px; /*position where enlarged image should offset horizontally */
}