Comment by jeroenhd

This is why I generally keep a mostly-clean browser around for development (only including some dev extensions). I've wasted half an hour when I had a stray uBO filter go off on a component I was working on once (wasn't even an ad) and that taught me a valuable lesson.

If you're testing a website, you've got to test it like your customers use it. I shake my head at the incompetence of web designers every time I encounter a website filled with scroll bars because the devs on macOS haven't bothered testing any other device.