How do I make an HTML table that doesn't have small gaps between rows?
 For example, if I create a simple table:

<table>
<tr>
<td style="float:left; padding:0px; background-color:#cccccc">Hello&nbsp;</td>
<td style="float:left; padding:0px; background-color:#cccccc">World!</td>
</tr>
<td style="float:left; padding:0px; background-color:#aaaaaa">Hello&nbsp;</td>
<td style="float:left; padding:0px; background-color:#aaaaaa">Again!</td>
</table>

...the cells connect seamlessly from left to right, but there's a thin
color gap between the two rows.  How do I get rid of this gap where
the background shows through?