I am using an ASP.net application as a PowerPoint add-in. While updating the application, if during that time add-in is accessed, then 404 error comes up in powerpoint. If I add app_offline.htm page for maintenance mode ( adding in root folder), then also it does not have any effect because while loading the add-in, the url being used is the home html page.
So can you please help me in showing a proper maintenance page while add-in is being updated instead of showing 404 error page, so that user is aware that application is being updated.