1. A method comprising: sending, by a first server of a plurality of servers in an origin domain of an online services system, a first web page in the origin domain to a user device, the first web page including a third party link, the third party link directed to a third party page of information in an external domain; detecting, by the online services system, a user selection of the third party link on the first web page; starting, by computer instructions from the online services system, a timer at the user device upon the user selection of the third party link; responsive to the user selection of the third party link, directing, by the online services system, the user device away from the origin domain to the third party page in the external domain, the third party page configured to be displayed on the user device; stopping, by the computer instructions from the online services system, the timer when the user device returns to a second web page in the origin domain, the second web page provided to the user device by a second server of the plurality of servers; providing, by the computer instructions from the online services system, to the origin domain information from the timer indicating a duration during which the user device was away from the origin domain; and receiving, at the origin domain from the computer instructions on the user device, the information from the timer indicating the duration during which the user device was away from the origin domain as a result of the user selection of the third party link.