Few months ago QA at my workplace found a bug with my work but I couldn't reproduce it. Turns out they're using Chrome and I'm using Firefox, and after reading some docs & specs, I concluded that Firefox's behavior is not correct. I'm about to file a bug and turns out that I found a same issue that's filed 20 years ago, and it's still open today: https://bugzilla.mozilla.org/show_bug.cgi?id=156090 Quite amusing...