1. A method comprising: receiving, by a server, a request from a client device to access a first content that is not available from a first Web domain; identifying, by the server, at least one interest keyword based on a combination of keywords that yield search results including the first Web domain and a user's clickstream data responsive to the search results; classifying, by the server, the first content that is not available based on the at least one interest keyword; identifying, by the server, a second web domain based on historical relevance data, and the classification of the first content that is not available, the historical relevance data including one or more previous attempts to access the first Web domain and session data representing activity performed with respect to the first Web domain; and transmitting, by the server, the at least one interest keyword to a server of the second Web domain, wherein the second Web domain serves second content similar to the first content and associated with the interest keyword to the user.
2. The method of claim 1 , wherein the server is an advertising server and the served second content includes an advertisement that is determined to be relevant to the at least one interest keyword.