The definition of the ordering of the Web pages, returned on a given query, is a crucial topic, which gives rise to the notion of Web visibility. A fundamental contribution towards the conception of appropriate ordering criteria has been given by means of the introduction of PageRank, which takes into account only the hyper-linked structure of the Web, regardless of the content of the pages. In this paper, we introduce a circuit analysis which allows us to understand the distribution of PageRank, and show some basic results for understanding the way it migrates amongst communities. In particular, we highlight some topological properties which suggest methods for the promotion of Web communities. These results confirm the importance and the effectiveness of PageRank for discovering relevant information but, at the same time, point out its vulnerability to spamming.