The RESTRICTIONS are constraints used to display BANNERS. That is, that for a PAGE and a POSITION we have a BANNER that is to be displayed by a certain number of times - called the initial number. A RESTRICTION contains the no. of times the BANNER was displayed and the no. of times left from the initial number. There can be more than one RESTRICTION on a PAGE and POSITION, and to choose the BANNER to display (the most appropriate RESTRICTION to apply) we use the rotational algorithm described below.