One of the rules of good HTML coding is that you should not have an empty table cell - it will give you a HTML error - that table will not show up in Netscape at all probably.
Try to add a & nbsp; (remove the space between & and nbsp; ) in the empty cell, or a transparent gif.
Try this:
Code:
<table width="100%" height="12%" border="0" cellpadding="0" cellspacing="0">
<tr>
<td valign="bottom">
<img src="bg.gif" height="15" width="100%">
</td>
</tr>
<tr bgcolor="#777777">
<td>
& nbsp;
</td>
</tr>
</table>
Remove the space between & and nbsp; (stupid vB.org parses it so it disappears as a space).