Originally Posted by ktmom
Without specifics, this is a general explanation.
Controlling how ads are served within browsers is not always in your control through DNS redirection. A website might embed the direct link that your device processes and makes a DNS request for. In this case, DNS reflect on the device will work to "block" the ad.
Or, a website might use scripting and handle the requests directly, serving the resultant ads directly to your browser without your device ever making a DNS call. Finally, any time a domain is called via an IP address, it will never go through DNS.
IMHO, the best way to deal with browsers is to use the uBlock origin plugin. I use it with Firefox, but I believe it's been discussed in this thread that there are now plugins available for other browsers.
As far as why you get differing results using a VPN, without knowing what website(s) are involved, my guess is the website behaves differently depending on where it thinks the user is located.
It's only about Google.com
At the top of the search results I get one or two Google ads. That's the only place.