If you have a look at the site I'm developing you can see that there's a slight displacement between the slide and its background. If you hover it gets worse.
This only occurs in Firefox and only on shows with more than one slide (i.e. where the navigation comes into play)
I've tried adjusting various display elements with no real success. I did manage to stop it displacing, by changing the nav display to inline, but the nav buttons no longer faded away and the larger gap at the top was then constant.