I see what you're doing here, but this feels brittle - what if the visitor is on a slow connection and Tabzilla is still not loaded for some reason?

One other issue that stands out in doing this, is you now have a `position:fixed` element that has a variable height (depending on if Tabzilla is open or closed). This could (possibly) cause issues with whatever parallax/scrolling stuff you have planned, as these effects sometimes need to calculate offset height from the viewport. It could likely be worked around though.