It just came to my attention that ads are not displaying for some people, and this is because they've added a space after putting in their Publisher ID.

Please make sure you put in your AdSense Publisher ID correctly and without any spaces! I've fixed a few of them but I can't get them all. If you check your AdSense account and have 0 page impressions, this could be why.

To edit your Publisher ID, go to "my account" -> "Edit" -> "Google AdSense Information".