Pop Up Image viewer FireFox/EI differ

[Tarak]

on my WebSite: www.mervynbeamishartist.com

In firefox the pop-up image come to the front - in IE it goes behind - is there any way to get around this and make it come to front in EI?

Thanks for a great CSS

[jscheuer1]

.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;
z-index: 100;
}