Okay, thanks to _Danny_B_ for pointing out that this completely breaks
with right floats. Floats will be needed to work nicely with floats,
but it's impossible to get floats to position precisely across
browsers, that I can see. I think the German way of doing it, with
the edit link on the left, has gone back to being the best choice,
although it might use these tabs if people like them more than the
bracketed link. (I'd sooner stick with the more traditional
brackets.)
Magnus, by the way, your script doesn't seem to work properly in
non-Firefox browsers. It highlights the sections, but then refuses to
un-highlight them when you hover out.