Reverse engineering techniques have the potential to support Web site understanding, by providing views that show the organization of a site and its navigational structure. However, representing each Web page as a node in the diagrams that are recovered from the source code of a Web site leads often to huge and unreadable graphs. Moreover, since the level of connectivity is typically high, the edges in such graphs make the overall result still less usable. Clustering can be used to produce cohesive groups of pages that are displayed as a single node in reverse engineered diagrams. In this paper, we propose a clustering method based on the automatic extraction of the keywords of a Web page. The presence of common keywords is exploited to decide when it is appropriate to group pages together. A second usage of the keywords is in the automatic labeling of the recovered clusters of pages.