If you ask me web browser's stole CTRL+S! It used to mean "save my work", but in a browser it means "download a copy of the website I am viewing", which seems totally different to me. I can't remember ever wanting that behavior.
I agree with you that websites shouldn't override useful browser behavior, but I'm OK with websites restoring CTRL+S to it's rightful meaning of saving my work.
Except, it generally doesn't mean that either. It means "download the page again and save that - nevermind if what I'm looking at has changed since it was retrieved". Which also breaks the mental model of "save my work", even if you're just typing text into a form.
I agree with you that websites shouldn't override useful browser behavior, but I'm OK with websites restoring CTRL+S to it's rightful meaning of saving my work.