After dedicating hours to this, I have identified and isolated the issue below. The first link does not underline on hover in Firefox, while it works perfectly in all other browsers tested. However, the second link functions properly in Firefox as well. Most of the existing HTML on the site follows the same structure, so a fix that applies site-wide would be greatly appreciated.
HTML: (cannot paste code here due to tag removal) http://pastebin.com/duqfKGeY
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>
FF test
</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<link href="ff.css" rel="stylesheet" type="text/css" />
</head>
<body>
<table>
<tbody>
<tr>
<td>
<ul type="disc">
<li>
<a target="_blank" href="http://example1.com">
<font size="2" color="#b80000"><b>Example Link 1</b></font></a>
<br>
<font size="2" face="Verdana">
example text example text example text example text example text example text example text example text example text example text example text example text example text example text example text example text example text
<a target="_blank" href="http://example2.com/">
<font size="2" face="Verdana" color="#b80000">Example link 2</font>
</a>
example text example text example text example text example text example text example text example text example text example text example text example text example text example text example text example text example text .
</font>
</li>
</ul>
</td>
</tr>
</tbody>
</table>
</body>
</html>
CSS:
a{color:#b80000;}
a:link{color:#b80000;text-decoration:none;}
a:visited{color:#b80000;text-decoration:none;}
a:hover{color:#b80000;text-decoration:underline;}
a:active{color:#b80000;}
Edit: Successfully validated without any errors on W3C Validator