The Site Online action will remove an app_offline.htm file in the root of the web site. This action can be placed after the updating work is performed, ensuring that the site is available to visitors when the update is completed.
Web root path
This is the local server path of the web root directory. When using the WebUpdatePostbackDisplay, the Application Directory will represent the web root. When using an admin utility, the web root can be set relative to the application directory (which would be the physical path of the utility application), or an Explicit Path can be defined as well.
The explicit path and the sub directory values support the use of Shared Properties. Any shared property used in the value will be expanded as the update is executed. Shared properties can be added delineated by $’s. (e.g $MyRootPath$ ).