1. A method comprising: analyzing, by a browser plug-in and during an initial loading of a structured document at a client device associated with a user, one or more elements of an object model representation of the structured document to identify one or more objects from a plurality of objects embedded within the structured document, wherein each of the plurality of objects comprises content and the structured document is a markup-language document that originates from a source external to a social-networking system and is displayable as a webpage; modifying, during the initial loading of the structured document at the client device, the object model representation of the structured document to display one or more controls, associated with the social-networking system, proximal to one or more of the one or more identified objects in the webpage from the source external to the social-networking system; detecting an interaction by the user with one of the one or more controls, in the webpage, associated with a particular one of the one or more identified objects; sending a message to the social-networking system, wherein the message comprises: (1) an identifier associated with the particular identified object and an identifier associated with the user, (2) instructions to augment a social graph associated with the social-networking system, the augmenting comprising adding an edge between a user node associated with the user and a node associated with the particular identified object, and (3) an indication that the user has been authenticated by the social-networking system; and receiving a response from the social-networking system indicating that the edge has been added to the social graph; and modifying the one of the one or more controls to indicate an association between the user and the particular identified object.