This isn't a big thing and I'm sure it's Firefox, not Floatbox, but I'm seeing some odd artefacts on the scrollbar in the FB window.

If you scroll with the mouse wheel they disappear after a couple of seconds. If you scroll by dragging the scrollbar thumb they disappear as soon as you let go of the thumb.

http://www.italianproperties.co.uk/test/info.html

Firefox 19

I don't see this as a big problem - just reporting this in case it's a symptom of a larger issue.

I pulled the image from your post because its large size distorted the forum page layout.

This is certainly a Firefox bug. It's in charge of rendering the scrollbars. But tests showed that it was happening only to div scrollbars in a floatbox, and not to similar scrolling divs on the host page. Slicing and dicing revealed that the trigger condition is the presence of the fixed-position translucent page overlay that's underneath the displayed div. If we hide or remove that overlay, the scrollbars render correctly.

I don't have a workaround for this problem. Perhaps I will put together a test case that doesn't involve Floatbox and submit it as a bug report to Mozilla. I'm not committing to doing that, as I really don't have a lot of time for such carry-on these days.