1. A method of reconstructing browser history for analyzing interactions with the Internet, comprising: receiving, by a computing system having one or more processors, a request from a client device for a first item of content, the request having a referrer field; retrieving, by the computing system, a referral tree having a first recorded node associated with the first item of content and a second recorded node associated with a third item of content, responsive to the request, the referral tree identifying a plurality of items of content, each recorded node in the referral tree associated with a request for items of content, each item of content comprising a portion of an online document; determining, by the computing system, that the first recorded node is not connected with the second recorded node; identifying, by the computing system, a synthetic node of the referral tree connected to the first recorded node based on the referrer field for the first recorded node and to the second recorded node based on the referrer field for the second recorded node; determining, by the computing system, that the synthetic node is connected to the first recorded node and the second recorded node; determining, by the computing system, based on the identification, that the client device has retrieved a locally-cached copy of a second item of content associated with the synthetic node of the referral tree without the recorded request for the second item of content transmitted via the computing device, responsive to determining that the first recorded node is not connected to the second recorded node and to determining that the synthetic node is connected to the first recorded node and the second recorded node; identifying, by the computing system, the online document comprising the first item of content and second item of content, responsive to the determination that the client device has retrieved the locally-cached copy of the second item of content; and recording, by the computing system, a request for the identified online document by the client device.