This has been in ToT for at least 6 months, i assumed it was going to go away like many other CSS regressions do, but alas it hasn't. View the given URL in both shipping WebKit 419.3 (Safari 2.0.4) and a ToT build. Notice how the left margin is bigger than it was before? The old WebKit renders the same as Opera and Firefox. I have some custom CSS for IE so ignore that in comparisons. I have been trying to figure out what it is without success, so I can't yet provide a reduction. Perhaps a fresh set of eyes can spot it (I can only stare at this CSS for so long before it becomes meaningless!)
Created attachment 12508 [details] ToT rendering
Created attachment 12509 [details] Old rendering
Created attachment 12510 [details] Opera 9 rendering