This demo appears at first glance to look correct, but when you actually look at table borders and cell borders, there's something very odd going on. The colors are off, and borders seem to be overlapping.

This is true. The borders look whacky.

I _think_ the testcase shows a simplified form of what is causing the errors on the test6.html page. Basically, if there is an inner table in a rowspanned cell, and the inner table has more than one row, then the rowspanning goes wrong (the algorithm has the wrong idea about the inner table dimensions). I cranked up the cellspacing to make the error more apparent (and it bears no resemblance to the original page).

*** Bug 6223 has been marked as a duplicate of this bug. ***

fixed with today's checkin.

Fixed in the June 2 Build.

*** Bug 7686 has been marked as a duplicate of this bug. ***

Disregard my previous comment (sorry about spam).