MISTAKE MONDAY for Jan.27: Can YOU spot what’s wrong?

Can you spot what’s wrong in the image below? Please post your answer as a comment. I post these challenges to raise awareness of the importance of proofreading.

Believe it or not, this mistake appeared on the AP Stylebook website. I imagined that website would have a rigorous proofreading process. The moral of the story is that everyone makes mistakes. (I know I make plenty of them.)

I tweeted to @APStylebook about the problem. Although no one responded to me, I see that the mistake has been corrected.