i was browsing someone's twitter and getting annoyed that the top nav followed me down the page, wasting a ton of vertical space

this well-named userscript changes such elements from fixed to absolute so they scroll away like everything else :)

userscript: Scroll Away
https://github.com/Aprillion/greasemonkey_scripts/blob/master/scroll_away.user.js

(will have to keep an eye on it to see if it breaks other sites in nasty ways, though)