Kill Sticky bookmarklet[1]. Also works on mobile. Get in the habit of clicking it, you'll start using it a lot to recover that extra inch of vertical space that web devs love to take away from you for some bizarre reason.
[1] https://github.com/t-mart/kill-sticky
NoScript[2] often prevents them from showing up in the first place, but it's a bit bigger lift to get used to using.