1. In a network environment that includes a plurality of nodes and that uses a markup language to create documents, a method for filtering the documents, comprising the steps of: upon receiving a request from a requesting node among the plurality of nodes, constructing an input Document Object Model (DOM) based on a document corresponding to the request storing the input DOM; identifying elements of the input DOM that have previously been stored; and filtering the input DOM to obtain a filtered DOM, based on at least one pre-specified rule being applied to the input DOM.