Something that I do that most people seem to miss is disable sticky headers below a certain height. It's super easy to do with a simple media query.
I used to use a square-screened BlackBerry 10 device, and the number of websites that didn't do this was infuriating, and I made frequent use of a "Kill Sticky" bookmarklet. But everyone runs into this issue at some point just by turning their phone to landscape mode, which most web developers evidently don't test with.
I came here to bring this up, I use a Key2 daily and have used a UniHertz Titan for a time. Many applications don't handle odd screen aspects very gracefully. (Like Instagram opting for zooming stories instead of lettering).
I used to use a square-screened BlackBerry 10 device, and the number of websites that didn't do this was infuriating, and I made frequent use of a "Kill Sticky" bookmarklet. But everyone runs into this issue at some point just by turning their phone to landscape mode, which most web developers evidently don't test with.