<style type='text/css'>

.img-thumbnail{
position: relative;
z-index: 0;
}

.img-thumbnail:hover{
background-color: transparent;
z-index: 50;
}

.img-thumbnail span{
position: absolute;
background-color: #ffffff;
padding: 5px;
left: -1000px;
border: 1px solid #000;
visibility: hidden;
color: black;
text-decoration: none;
}

.img-thumbnail span img{
border-width: 0;
padding: 2px;
}

.img-thumbnail:hover span{
visibility: visible;
top: -100px;
left:100px;
}

</style>

<a class="img-thumbnail" href="#">
<img src="link ảnh1" border="0" height="98" width="130"/>
<span>
<img src="link ảnh1"/>
</span>
</a>