There's 'Why are there gaps between image rows in tables when the layout engine is in the Standards mode?' in Mozilla Web Developer FAQ (And here's more detailed explanation)
I also saw this issue mentioned in meyer's 'CSS: The Definitive Guide'.
But I've tested it on firefox 10.0.2, ie8 and chrome 17.0.963.56, and all resulted in no gaps at all.
Here's the tag I used.
<table>
<tr>
<td style="padding:0; background-color:red;">
<img src="https://developer.mozilla.org/@api/deki/files/718/=Images-tables-gaps-figure1.gif" />
</td>
</tr>
</table>