| 摘要 |
<p>Systems, methods and apparatus are provided including a method that identifies when a content item that was presented to a user in association with a slot on a resource is not visible to the user, wherein the slot presenting the content item is rendered wholly or partially not visible as a result of user activity. The method further includes receiving a request to provide an alternative content item to be presented to the user when user activity enables re-presentation of the slot and delivering the alternative content item to a device associated with the user responsive to the request.</p> |
