Are you sure its not just an ad-blocker or something similar in Norton? Or do you still see the video but get a big gap as well?
That code looks weird anyway.
Percentage padding refers to the width of the container even for top and bottom padding (unlike percentage heights which refer to the height of the containing block)
Do you have a link that we can try out and see if we can spot anything untoward (and possibly a screenshot of the problem with Norton on and then off).
I think that code is a pretty standard way of making a responsive 16:9 video embed, no?
Ah, ok it is the width that it is wanted for scaling so the padding percentages is ok. You can rely on Thierry’s techniques to work as he is very thorough so that method should be ok.