An ad pops up on every page which blocks part of my view. Only on DU.

[Make7]

8. Strange, you can see the border the Ad is intended to occupy.

I thought Google Ads were supposed to determine the Ad container size and serve something that fits.

You might try zooming the page in (Ctrl +), out (Ctrl -), or no zoom (Ctrl 0) to see if that makes a difference. Also try reloading a DU page without using cached content (Ctrl Shift R) in case there is some error in your cached stylesheet for DU. And if you haven't tried already, quit the browser and reopen.

Honestly, that looks like Google is just serving up Ads that are the wrong size. But as a precaution you should run a virus and malware scan to make sure something else hasn't appropriated that Ad space.

Unfortunately I don't really know anything about Chromebooks and I rarely use Chrome so I can't offer much advice. I would suggest posting about this in the Ask The Administrators forum to see if they can contact Google to try to resolve it - if it's happening for you, it's probably affecting others as well.