Thread: "This ad has already been published or you do not have permission to activate this ad

"This ad has already been published or you do not have permission to activate this ad

When I was adding new pages, without knowing I thought "add new" page is a sample page that can be used to make a new page! So I edited that page and renamed it to another page name and put my text into it! then I had this problem:"This ad has already been published or you do not have permission to activate this ad. Please contact the site admin if you are experiencing any issues."
I finally remembered the cause of this error in my case and now I want to fix it. I added a new page named "add new" and the error is gone but it is only a blog page not like the one we had and were able to post an item. which file should I replace to return back to normal?
Thanks