They probably use Javascript to hide/show the navigation bar as you scroll and my guess is that they set its position with Javascript instead of CSS.
Knowing the state of modern webdev that is probably exactly what happens
Javascript was a mistake.
Nah, uneducated agile development is always a mistake. Just because something “works” doesn’t mean it works correctly or efficiently. Many people wrongly believe agile development goes so far as to say you should move on the moment something works. So, when someone implements something in a piss-poor manner, these types simply test it in the most common usage case, see that it “works”, and move on. Executives see that it “works” and assume they have fully competent devs. Cycle of shitty products continues.
Could also simply be from a dev that doesn’t realize how far CSS has come since the old days where basic styling was about it.
I had bottom-bars appearing around 3/4 of the way down the screen on Firefox on my Android and never did find the actual cause (scoured about:config but no luck) but I solved it by clearing data and starting a new profile.
First I forced closed the app and backed up the file with my tabs using a file manager with root access:
/data/data/org.mozilla.firefox/files/mozilla_components_session_storage_gecko.json
Then cleared the data, launched it and signed in and such, forced it closed again, copied back the tab session file, and launched it again.
I just tried their site in fennec w/ NoScript and only have their main domain whitelisted. That bar appears at the bottom for me. Not sure what’s going on here.