<script language = "JavaScript">
function showLinkImage(id) {
document.getElementById(id).style.display = "block";
}
function hideLinkImage(id) {
document.getElementById(id).style.display = "none";
}
</script>

<table align="center">
<tr>
<td align="center" valign="top">
<a href="#" onmouseover="showLinkImage('float_1')" onmouseout="hideLinkImage('float_1')">TEST 1</a>
<div id="float_1" style="display: none; position: absolute;">
<img src="Test2.jpg" alt="test1" />
</div>
</td>
<td align="center" valign="top">
<a href="#" onmouseover="showLinkImage('float_2')" onmouseout="hideLinkImage('float_2')">TEST 2</a>
<div id="float_2" style="display: none; position: absolute;">
<img src="Test1.jpg" alt="test2" />
</div>
</td>
</tr>
</table>