I will explain what I tried because I can't get it to work.
I created a plugin:
Plugin Title:
AdSense Top Banner
Plugin Location: showphoto_top
Plugin Code:
Code:
Content visible to verified customers only.
I do not see the words "ADSENSE CODE" appear after I saved this.
Then when I edit the plugin I see it automatically added more reverse slashes:
Code:
Content visible to verified customers only.