Ok, a little more about framesets.
Framesets don't have a document body and can't display content directly. They can only contain frame documents. In order to cover the whole page, floatbox attaches to the top page document. In a frameset, there's nothing there on the top page to attach to.
IE is the odd man out here. It will render content attached to a top frameset document. This is actually an odd thing for it to do, and is counter to the way framesets are intended to work. No other browser does this. Firefox, Safari, Chrome, Opera, SeaMonkey - your site won't work with any of these. Something that works in only one browser is no good.
You can use framebox.js instead of floatbox.js inside your frameset child docs if you like. If you do this, the floatbox display will cover just the frame portion of the page, and not the entire page. Read up in the docs on this if you're interested.
If you really want a framed layout, use iframes instead. Floatbox works fine with these, and iframes replaced framesets as the generally preferred method some years ago. You can also freeze a navigation div by giving it fixed positioning. But don't be thinking you're going to drag me in to helping with site design or general web-site building tips. I'm here for floatbox support only.