remove the app_offline.htm

 
I get the message "This application is currently offline. To enable the application, remove the app_offline.htm file from the application root directory. "
 However, this is no app_offline.htm file in the root directory.  Where in the heck is it?
I am looking in the Solution Explorer, and I also looed in Windows Explorer . . . not a sign of it.   ??? 
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