A computer-implemented system and method for keyword extraction and contextual advertisement generation are disclosed. The system in an example embodiment includes a keyword extraction service to obtain information related to user activity on a host site and to extract relevant keywords from content of a web page, the information related to user activity on the host site being used to determine relevancy of the extracted keywords, and a contextual advertiser to produce an advertisement placement on an affiliate web page, the produced advertisement placement being relevant to user activity on the host site.