Table not resizing the way it should

[MrGecko]

I'm trying to make the table resize. The two that have width="15" are on the sides, and I want them to stay at 15, but they keep changing when I type more text in the middle table. How can I prevent this?

<table width="140" height="52" border="0" cellpadding="0" cellspacing="0">
<tr>
<td width="15" background="l.png">&nbsp;</td>
<td valign="top" align="center" background="c.png"><table border="0">
<tr>
<td>&nbsp;</td>
</tr>
<tr>
<td align="center" valign="top"><font color="#FFFFFF">Login</font>&nbsp;&nbsp;<font color="#0066FF">&bull;</font>&nbsp;&nbsp;<font color="#FFFFFF">Singup</font></td>
</tr>
</table></td>
<td width="15" background="r.png"> &nbsp; </td>
</tr>
</table>

[MrGecko]

I fixed it with this

<table height="52" border="0" cellpadding="0" cellspacing="0">
<tr>
<td width="15" background="l.png">&nbsp;</td>
<td valign="top" align="center" background="c.png"><table border="0">
<tr>
<td>&nbsp;</td>
</tr>
<tr>
<td align="center" valign="top"><font color="#FFFFFF">Login</font>&nbsp;&nbsp;<font color="#0066FF">&bull;</font>&nbsp;&nbsp;<font color="#FFFFFF">Singup</font></td>
</tr>
</table></td>
<td width="15" background="r.png"> &nbsp; </td>
</tr>
</table>