1. In a computing environment, a method comprising: detecting repetitive regions on forum web pages, wherein each repetitive region comprises a block area that includes multiple data records in a uniform formation; generating a pattern from each repetitive region, wherein each pattern is an abstract representation of the multiple data records of its corresponding repetitive region; determining which forum web pages have similar regions with which other of the forum web pages based on the patterns, wherein the determining comprises extracting a feature set from each forum web page including region-based features, and wherein the feature sets include the generated patterns, and wherein the feature sets comprise locations of the repetitive regions, sizes of the repetitive regions, and occurrence frequencies of the patterns; and clustering forum web pages into categories based on their similar regions.