Excuse the bad ASCII, but the page is laid out like this: ------- |--1--| ------- |--2--| ------- |3|-4-| ------- |--5--| 1. Will scroll normally and d

Excuse the bad ASCII, but the page is laid out like this: ------- |--1--| ------- |--2--| ------- |3|-4-| ------- |--5--| 1. Will scroll normally and disappear from the view port. 2. Will scroll a little bit, then become sticky 3. Will over scroll a little bit at the start (the gap between "human interface guidelines" and "overview" is bigger at the very top), then become sticky until you get near the bottom and will then become sticky again. 4 and 5. Will scroll normally. This goes beyond sticky elements, it's sometimes sticky, sometimes moving elements, It's unexpected and confusing behavior. Not confusing enough that anyone will get lost, but confusing enough that your eye's get drawn to other parts of the page because they start/stop moving as expected at various times.