Let me know if there's any difference.
Incidentally, to test it still worked, I reloaded the page in Safari without noticing it was set to full screen. Aside from the usual problems there was one area that crashed, with one item overlayed over another.
This was corrected by changing to a window. As I said before, if I move the margins closer together the formatting is correct. Ashton also noticed that the margin position had a significant effect.