Instead of one rule or rule set per targeting item, a multisite environment supports default rules, site override rules, and site group override rules.
Default Rules
Each user segment or content group has one default rule. A targeter has one default rule set group.
The default rule is required; it cannot be deleted. The default rule executes on the current site (the site the visitor is on), unless a site or site group rule overrides it. If one or more site override rules, collectively, specify all the sites, the default rule never executes.
Site Override Rules
Site override rules execute on one or more sites that you specify. This enables you to specify different behavior on different sites.
Site override rules must meet the following requirements:
A site override rule must specify at least one site on which it executes.
Two site override rules for the same targeting item cannot execute on the same site.
Site Group Override Rules
Site group override rules execute on one or more site groups that you specify. This enables you to specify different behavior on different site groups.
Site group override rules must meet the following requirements:
A site group override rule must specify at least one site group on which it executes.
Two site group override rules for the same targeting item cannot execute on the same site group.
