if you create a file named AppOffline.htm in the root directory of the web site user will be redirected to the page. This is useful when we upload something in PROD. We can create a file named AppOffline.htm specifying “site is upgrading………. Please wait for few mins….”, copy it in the root directory of web site and then we can modify PROD files.
So when we need to update the live site content for few moments then we can put the file in the root directory and the site will be offline. Any user trying to access any url of the site will get the appoffline.htm file.. Then when update will be done then the file can be deleted to bring the site online.