Image problems in HTML, FF specificly

[stin]

I'm having an issue with images not displaying in Firefox, but showing up in IE8. I'm not getting the Red X or broken path image, I'm just not getting anything. When I 'View Source' in FF, I can click on the picture link and it opens fine.

I've tried saving the pictures as .jpg that didn't seem to help any.

<tr>
	<td>
	   <a href="full_images/muscatine_advert.pdf"><img src="thumbnails/muscatine_advert.png" border="0"/></a>
	   <a href="full_images/indiana_advert.pdf"><img src="thumbnails/indiana_advert.png" border="0" /></a>
	   <a href="full_images/indiana_advert_2.pdf"><img src="thumbnails/indiana_advert_2.png" border="0"  /></a>
	</td>
	<td width="326" height=2><span class=title>Business Journal Ads</span></td>
  </tr>

I've attached 2 screenshots. The page in question is behind some login stuff, so that's the best I can do. Any thoughts on this? It's really got me stumped.

BTW, this is a legacy site that is going away soon-ish, so it's not worth re-writing to get rid of the tables