<table width="50%" style="background-image: url('./img/test1.gif')" id="back">
<tr>
<td>
<div onmouseover="document.all['back'].style.backgroundImage='url(./img/test2.gif)'" onmouseout="document.all['back'].style.backgroundImage='url(./img/test1.gif)'">■カーソルをここに合わせてください。</div>
</td>
</tr>
</table>