To provide an information processor which adequately can display a window application according to a screen size, its display method, and a storage medium.

An image display property, based upon the contents of the image display property having a value matching with a display indication property 202 stored in the window application 201 is selected out of the image display properties regarding an image display of the information processor 101. When the image display property having the value matching with the display indication property 202 is not present, an image display property having a value closest to the display indication property 202 is selected. According to the image display property which is thus selected, the window application 201 is displayed on a display device 104.