.thumb {
position:relative;
top:0;
left:0;
}

.thumb a {
margin:0;
text-decoration:none;
}

.thumb a:hover {
background-color:black;
}

.thumb a .grand {
display:block;
position:absolute;
width:0;
}  

.thumb a:hover .grand {
position:absolute;
top:80px;
left:0;
width:300px;
height:225px;
}

chose