1. A method comprising: by a server, receiving an identification of one or more objects or references to the objects embedded in a structured document displayed on a client computing device to a first user, wherein: the structured document is a markup-language document displayed as a webpage; and the objects originate from one or more sources external to a social-networking system; by the server, accessing a social graph of the social-networking system to: determine if one or more second users having an association with the first user have accessed or are accessing any of the identified objects; and retrieve, from the social-networking system, one or more social-network data elements comprising social-network profile information provided by one or more of the second users to the social-networking system; and by the server, sending to the client computing device one or more instructions to modify, for at least one of the objects, the structured document displayed as a webpage to the first user to indicate that the object embedded in the structured document and originating from the sources external to the social-networking system has been accessed or is being accessed by one or more of the second users, wherein modifying the structured document comprises displaying, proximal to the object, one or more of the social-network data elements.