From MozillaZine Knowledge Base
To avoid a large number of pop-ups or a never-ending loop of pop-ups from a malicious site, Mozilla applications limit the number of pop-ups a non-click event is allowed to spawn. This preference specifies that limit.
Possible values and their effects
The number of pop-ups to allow from a single non-click event. (Default: 20).
First checked in
Has an effect in