a.testthumb span{ /*CSS for enlarged image*/
position:absolute;  /*set to fixed to prevent scrolling of the display box*/
visibility: hidden; /* hide it until hovereed over*/
background-color: white;
border:1px solid #dedede;
text-decoration: none;
}

a.testthumb:hover span{ /*let image show on hover*/
visibility: visible;
z-index: 1;
}