Maybe dupe of Bug 175190? But wouldn't you first need to set cellpadding=0 cellspacing=0 border=0 for your table to get a correct testcase (also when it might be a dupe)?
I think, this is not a dupe. I didn't dig enough in CSS2 specs, but I think, that Gecko renders row with display:block correctly. Why IE does it different (the "right") way? Because of way it's support CSS2. It doesn't support CSS2 specs for 'display' element (ie6 still doesn't). The bug is that empty space left after changing TR style.display property to 'none'.
The testcase looks very similar to the one in bug 206516: https://bugzilla.mozilla.org/attachment.cgi?id=147399&action=view
one should toggle between display:none and display:'' and bot block see my comment in bug 97506 *** This bug has been marked as a duplicate of 97506 ***