Firefox 24.0 on Ubuntu amd64 (raring). Looks like same problem as described in parent. Have a look at http://imgur.com/SfdVQ7k -- screenshot taken with a brand new profile.
Same problem here with Firefox 27 (Nightly).
Thanks for the screenshot, I'll fix that ASAP.
Looks perfect for me on Chrome on Windows, but I think I'd keep it fully expanded for a second or two or start out fully collapsed. Opening the tab to see something collapsing the instant it loads is a little ugly. Otherwise it's super-cool. A bit mystery-meat-ish, but your personal page is a good space for that kind of form-over-function.