Firefox 4 does have some changes to its table border code. Can you link to a page that shows the problem?

Sorry, it's proprietary info on an intranet.

I have not installed FF 4 yet so I do not know how it looks like. Howver, you can see three tables in the related support request on twiki.org, SID-01162.

It is also not clear if Jon is using the default skin of TWiki, or if the issue is with a custom skin of TWiki. TWiki.org has the default skin.

I can now verify that there are some issues with table border colors on FF 4. I added a number of screenshots to SID-01162 that illustrate the issue on FF 4.

I looked at the table at the bottom of the above linked page. The style rules affecting cell border colors just don't seem to apply to this particular table. Some of the rules are very close, but not a perfect match on the selectors for the th and td elements. Perhaps the old border-collapse code applied the table's border-color to the th and td elements as well?? That may have been a mistake.

TABLE:

<div class="twikiForm">
 <table class="twikiFormTable" border="1">
  <tbody>
   <tr>
    <th class="twikiFormTableHRow twikiFirstCol" colspan="2"><a 
href="/cgi-bin/view/Support/SupportForm" class="twikiLink">SupportForm</a></th>
   </tr>
   <tr valign="top">
    <td class="twikiFormTableRow twikiFirstCol" align="right"> Status </td>
    <td>Asked</td>
   </tr>
   <tr valign="top">
    <td class="twikiFormTableRow twikiFirstCol" align="right"> Title </td>
    <td>Tables rendering funny in Firefox 4</td>
   </tr>
...

  </tbody>
 </table>
</div>

CSS:

.twikiTable,
.twikiTable td,
.twikiTable th {
  border-color:#e2e2e2;
}

.twikiEditForm .twikiFormTable,
.twikiEditForm .twikiFormTable th,
.twikiEditForm .twikiFormTable td {
  border-color:#e2e2e2;
}

.twikiAttachments table,
table.twikiFormTable {
  border-color:#e2e2e2;
  background-color:#fff;
}

This is not the exact same problem but it is related.

Example Page: http://dl.dropbox.com/u/7520799/HTMLPage.htm

Forum thread where I describe the problem: https://support.mozilla.com/en-US/questions/825230

Here's a workaround: use the table plugin and specify tablerules="all". So at a minimum, include this directly before your table:

%TABLE{ tablerules="all" }%