[lbatx]

Many sites use dozens of domains. Some (probably most) are ads, tracking, and the like. But much of it is stuff needed to run the site. I don't think there is a reasonable set of defaults other than things not on an ad blocker blacklist. And asking the user to approve each domain on a page is too much -- how would they decide, and how would they know which one prevented the site from working properly?

[jackfraser]

What if that's fundamentally a flawed way of building things? Maybe your site should provide all of the assets it needs...

[lbatx]

It's certainly flawed, but providing all of the assets creates a different class of problems. Both approaches have pros and cons, plus the original comment I replied to passed it off as a solution to the problem at hand, which it's not.