According to some embodiments of the present invention there is provided a system of rule generation for web pages selection mechanism comprising a pattern recognition unit which analyzes a plurality of network requests and identifies a plurality of repeated patterns of characterizing features therein, a calculation unit which computes, for each said repeated pattern, a plurality of statistic features, and a rule construction unit which generates a plurality of web pages selection rules for at least some of said repeated patterns, wherein each of the web pages selection rules comprises a rule condition defining at least one criterion for matching it with characterizing features associated with at least one additional network request and a target web pages selection distribution set according to respective statistic features.