Google AdSense seems to be testing placing the ad choices arrow on the left top of the ads, instead of the top right of the ads.
A WebmasterWorld thread has complaints from some publishers, claiming the arrow, when positioned at the top left, covers part of the text in the ad itself. One AdSense publisher said:
Just noticed a small blue right-facing triangle in the left side of my leaderboards URL when viewing my site in iPad. I've refreshed and changed enough pages to know that at least in my account, this is being served up from AdSense. Anybody else seeing this?
Others are seeing this as well, but I am personally not able to replicate it on my own devices.
I photoshoped what they may see:
I wonder if this is a test or a bug with Google or the publisher's own site?
Forum discussion at WebmasterWorld.
Update: Here is a screen shot showing the issue, and it does seem to be a bug: