I’ve seen sites with those being fake. If you say “no” to the browser prompt, the website can’t ask again. But if you make a fake prompt, you can repeat it any time you like. (Agreeing becomes a two-step process. Who the hell wants notifications from 99% of websites though?!)
Immediately, but only because most web sites think it's OK to show all of these things at once, making it a good 2 second task to work out which parts of the page is the content (if any).
