1. A system configured to serve base content and relevant content to a user system based on an association of a user profile and the relevant content, such that the relevant content is relevant to a user, the system comprising: a plurality of web servers configured to serve the base content and the relevant content to the user system; a set of additional-content servers configured to serve the relevant content to the web servers if units in the user profile match units associated with the relevant content; a parsing server configured to, in response to a request for the base content from the user, extract the units from the base content requested by the user and after extraction of the units, generate the user profile on the basis of the units extracted from the base content requested by the user, generate a ranked list of the units in the user profile that are in the base content based on at least one of a relevance score and a revenue-generation amount for each unit in the user profile and calculate overall-relevance score for the units in the user profile based on the relevance scores and the revenue-generation amounts; and a unit-matching module configured to determine whether the units in the user profile, having overall-relevance scores greater than or equal to a threshold score, match units associated with the relevant content if the user requests the base content, wherein the web servers are configured to serve the base content and the relevant content if the units in the user profile match units associated with the relevant content.