1. A method comprising performing a machine-executed operation involving instructions for grouping structurally similar pages, wherein the machine-executed operation is at least one of: A) sending said instructions over transmission media; B) receiving said instructions over transmission media; C) storing said instructions onto a machine-readable storage medium; and D) executing the instructions; wherein said instructions are instructions which, when executed by one or more processors, cause the one or more processors to perform the steps of: for a sample of pages from each of a plurality of groups of Web pages, wherein the pages within a group are grouped together based on similarity of the pages, computing a respective distance of structural similarity between features within each sample page and the features within the other sample pages from the plurality of groups, and computing a radius of influence for each sample page, wherein the radius of influence for a sample page is based on the distance of structural similarity between the features within the sample page and the features within a nearest neighboring sample page; determining for each sample page, influential sample pages, from the other sample pages from the plurality of groups, whose distance of structural similarity from the sample page is within the radius of influence for the sample page; identifying, from the plurality of groups, one or more candidate group pairs whose constituent groups are a candidate for merging based on the sum of (a) a first summed distances of structural similarity between the sample pages from a first group of a group pair and the influential sample pages from a second group of the group pair, and (b) a second summed distances of structural similarity between the sample pages from the second group of the group pair and the influential sample pages from the first group of the group pair; computing intra-group compactness of each group from a first candidate group pair; computing inter-group compactness of the groups from the first candidate group pair; and determining whether to merge the groups from the first candidate group pair based on the intra-group compactness and the inter-group compactness.