.gallerycontainer{

position: relative;
/*Add a height attribute and set to largest image's height to prevent overlaying*/
}

.thumbnail img{
border: 1px solid white;
margin: 3px 5px 5px 0;
}

.thumbnail:hover{
background-color: transparent;
}

.thumbnail:hover img{
/*border: 1px solid blue;*/
}

.thumbnail span{ /*CSS for enlarged image*/
position: absolute;
/*background-color: lightyellow;
padding: 5px;*/
left: -1000px;
/*border: 1px dashed gray;*/
visibility: hidden;
color: black;
text-decoration: none;
}

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

.thumbnail:hover span{ /*CSS for enlarged image*/
visibility:visible;
top: 0;
left: 495px; /*position where enlarged image should offset horizontally */
z-index: 50;
}