Server.MapPath(".")1 returns the current physical directory of the file (e.g. aspx) being executed
Server.MapPath("..") returns the parent directory
Server.MapPath("~") returns the physical path to the root of the application
Server.MapPath("/") returns the physical path to the root of the domain name (is not necessarily the same as the root of the application)
If Path starts with either a forward slash (/) or backward slash (), the MapPath() returns a path as if Path was a full, virtual path.