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Used within a rule's conditions element to match elements that are containers or are contained within another element. Both the container and child attributes may use variables.
Properties and Methods:
Properties and Methods inherited from XUL Element
A variable reference to a node that is expected to be a child of the element that is referred to by the container element.
A variable reference to a node that is expected to be a container. If the variable is the same as the uri attribute on the content element, the resource must be a container element in order to match.