Okay, I’ve actually implemented this on my site, the hard way. If you go there you’ll see a floating menu at the upper right hand corner. It is part of a Text widget. Click on (for instance) “What’s happening to you” and it’ll take you to that page, with a new floating menu where that topic is expanded. The new floating menu has a higher z-index so as to conceal the globally available Text widget.
I laboriously went to every page (not including blog entries) and put in a box corresponding to that page. The job is done, but it’s still a nuisance because I’ll have to go through it all again whenever I add a new section.
Is there any way to get this effect in CSS with just the one Text widget?