A WebmasterWorld thread reports some Google AdSense publishers complaining that Google is adding borders around the ads they place on their web sites.
One AdSense publisher said:
Perhaps it's just me, but twice now I've seen my Adsense Ads with a border. This happened on two different domains.
What is strange, is that I did not make any changes to the ads and I originally set them up without a border. In both cases, they go back to borderless ads if I refresh. If I refresh again, it won't happen and seems to be simply by chance that I'm catching it.
I believe Google tested adding black borders around AdSense ads back in 2008.
I personally see a black border around the AdSense ad on my personal blog but I am not sure if I added it myself or not.
Anyway, publishers do not want to be forced into specific designs for the ads they place on their web sites. Google has been pretty good at giving flexibility on the ad formats and colors. So I am not sure what is going on here.
Forum discussion at WebmasterWorld.