OK... Hat perfekt funktioniert.
Hier mein Code - für den, den es interessiert.
<script language="JavaScript" type="text/javascript">
<!--
function offDiv(element){
document.getElementById(element).style.display = 'none';
}
function onDiv(element) {
document.getElementById(element).style.display = 'block';
}
//-->
</script>
<!-- x1.jpg ist 10px x 10px -->
<div style=" position:relative; padding:30px; height:50px; width:50px; background-color:#00FF00">
<div style="position:relative; float:left"><img src="pics/x1.jpg" onMouseOver="onDiv('1');" onMouseOut="offDiv('1');">
<div id="1" style="display:none; position:absolute; top:10px; left:10px;"><img src="pics/x1.jpg" width="30" height="30"></div>
</div>
<div style="position:relative; float:left"><img src="pics/x1.jpg" onMouseOver="onDiv('2');" onMouseOut="offDiv('2');">
<div id="2" style="display:none; position:absolute; top:10px; left:10px;"><img src="pics/x1.jpg" width="30" height="30"></div>
</div>
<div style="position:relative; float:left"><img src="pics/x1.jpg" onMouseOver="onDiv('3');" onMouseOut="offDiv('3');">
<div id="3" style="display:none; position:absolute; top:10px; left:10px;"><img src="pics/x1.jpg" width="30" height="30"></div>
</div>
</div>