A powder container includes a body and a pair of walls that blocks one longitudinal end of the body and the other longitudinal end of the body. in the screen of the web browser, that is not used for displaying information from a server, is used for displaying advertisements, during a period of time for which function commands are not inputted, thereby improving effectiveness of advertisement. An interval between times when the output data indicating the successive extremums and an elapsed time from the detection of the extremum is measured. A rope, normally stored on a spool removably attached to the base, may be used to reposition the base on the roof.