Systems and methods include those for serving advertisements contextually-relevant to an initial web page. Terms are selected from an initial web page that may later be used as representative keywords to select advertisements that are contextually relevant to the initial web page. In order to reduce the number of keyword candidates to a manageable number and to improve accuracy, keyword candidates are filtered via a series of operations that include: querying a network for web pages where the one or more keyword candidates are found, filtering the web pages based on time/date characteristics and a pre-defined number of web pages, analyzing the web pages using the one or more keyword candidates, and selecting certain keyword candidates to be representative keywords based on the analysis. The one or more representative keywords may be used to select one or more advertisements that may then be served with the initial web page.