[Plugin: PhotoContest Plugin] Weird error message

After rating a photo we get the following message…

Please add a class content_wppc to the div in the template!

Now, not being a programmer but rather what I refer to as a web mechanic, I can guess and trial and error thru some ideas, but any diection you can offer in resolving this would be appreciated.

the wp photo contest is running at https://fidoscityguide.com under menu item contests.

https://www.ads-software.com/extend/plugins/wp-photocontest/