Google’s PageRank algorithm is one of the most important pieces of the technical SEO puzzle. For a long time it formed the basis for their ranking methodology, and while it is not as crucial as it once was, understanding PageRank still gives us a valuable insight into the way search rankings work and the true value of different link building strategies. None of the major search engines release the complete technical details of their algorithms, but PageRank is perhaps the best known ranking device.
PageRank is based on the fundamental idea that the internet is a network of sites connected by links. Imagine a small part of that network with a dozen or so sites of various sizes. Then do some mental link building until all the sites are connected to the others, some by one link, some by more. Now picture a user clicking randomly though the links. It stands to reason that they will end up on sites with a lot of inbound links fairly frequently, and sites with relatively few inbound links won’t be visited so often. But what if one of the bigger, more popular sites has only one outbound link, leading to a smaller site? That site will get just as many visits as the big one, because the traffic has nowhere else to go.
There is a lot more to PageRank, but that last point tells us exactly why good link building services place so much emphasis on quality over quantity. A link from a site that nobody visits is worth nothing, and will do nothing to improve your site’s PageRank or search rankings (or bring in traffic, for that matter). A single link from a highly popular site that doesn’t hand them out easily will boost PageRank significantly, and can make very significant changes to rankings.