Application Offline

In order to take the Application/Website offline you can perform the following operation.  

Browse to the location you have the Application/Website installed.  

Find the file named '_App_Offline.htm'

Rename this file to 'App_Offline.htm'.  You are removing the first underscore.

Application Online

In order to take the Application/Website online you can perform the following operation.

Browse to the location you have the Application/Website installed.

Find the file named 'App_Offline.htm'

Rename this file to '_App_Offline.htm'.  You are placing an '_' at the beginning of the filename.