Automatically generated content is ubiquitous in the web: dynamic sites built using the three-tier paradigm are good examples (e.g., commercial sites, blogs and other sites edited using web authoring software), as well as less legitimate spamdexing attempts (e.g., link farms, faked directories).Those pages built using the same generating method (template or script) share a common "look and feel" that is not easily detected by common text classification methods, but is more related to stylometry.In this work we study and compare several HTML style similarity measures based on both textual and extra-textual features in HTML source code. We also propose a flexible algorithm to cluster a large collection of documents according to these measures. Since the proposed algorithm is based on locality sensitive hashing (LSH), we first review this technique.We then describe how to use the HTML style similarity clusters to pinpoint dubious pages and enhance the quality of spam classifiers. We present an evaluation of our algorithm on the WEBSPAM-UK2006 dataset.