a.screen, a.screen:visited {
color:#c00; 
position:relative; 
z-index:1;
}
a.screen b {
position:absolute;
visibility:hidden; /* hide the image */
width:400px; /* give it a width */
height:0; /* no height to solve an Opera bug that 
             makes it selectable when hidden */
border:1px solid #000; /* add a border */
left:0; /* position:the image */
top:-280px;
}
a.screen:hover {
text-decoration:none; 
border:0; /* needed for this to work in IE */ 
z-index:1000;
}
a.screen:hover b {
visibility:visible; /* make the image visible */
height:268px; /* now give it a height */
cursor:pointer; /* for IE */
z-index:500; 
}
a.screen:hover b img {
border:0; /* remove the link border */
}