Onmouseover change image

Hi,

A simple question. In a webform I placed 3 images

<table id="TABLE1" >

<tr>
<td colspan="2">
<asp:Image ID="Img3" runat="server" Width="250px" /></td>
</tr>
<tr>
<td >
<asp:Image ID="Img1" runat="server" Width="100px" />
</td>
<td >
& ...