And here it is. I used to wonder why they didn’t already do this.
They can do this the same way ads become “placements” in movies. In a movie, whenever the camera zooms in on a bag of potato chips, or a soda, or the actor exclaims how good his exercise equipment has been for staying fit, you can bet it’s a product placement, a commercial ad. It did not require the cinema or the cable channel or you smart TV or your computer to put it in there, they did it at the studio.
Now, the reason they can let the third parties do their dirty work in a browser is that the browser can pull in third-party content from somewhere else. That’s easier and maybe cheaper because they deal with some ad agency or some commercial browser to place it everywhere. But work it out so each individual person or company serving up web pages incorporates it. An ad agency can easily handle this, but if it comes in the page served directly b the web page creator, popups can’t know the difference.