stedata (Steve Ste) on "Error, no Ad ID set! Check your syntax!"

My business depends on ads in my blog. It is my livelihood. However, I feel like I am constantly leaving messages here that are never retued. How does this work? I currently have that "Error, no Ad ID set! Check your syntax!" message on the "Preview" section when I go to add an ad. What do I need to do to put more adverts on this site? Thank you.

What plugin, if any, are you using to place ads on your site?