Large online retailers look at thousands upon thousands of pages which have the opportunity to get crawled and indexed by the SERPs (search engine results pages). There are also near infinite choices for how you could interlink all those pages. Out of all those permutations, there is one configuration that is the most favourable from an SEO point of view. That’s because it maximizes the flow of link juice (PageRank) to the most important pages and minimizes (or cuts off completely) the flow of PageRank to the least important pages. The most important pages will generally have the most potential to rank highly for the targeted keyword phrases, to compel the searcher to click, and to drive that visitor toward a “conversion event” for example purchasing a product from the site.
To achieve the optimal configuration of your internal linking structure, one needs to think strategically about how to “spend” the link juice that has been bestowed on the site through inbound links.
Think of these inbound links as “votes,” and remember that we’re dealing with a meritocracy here, and not a democracy. In other words, not all “votes” are of equal value. Of all the pages of the site, it’s probably the home page that has earned the most and best votes and is the most endowed with PageRank. Therefore, the site’s hierarchical tree structure largely determines how the link juice is “spent”. So, I hope you organized your site tree with SEO in mind, not just usability!
One of the most powerful, and most underdeveloped, on-page SEO tactics is re-jigging your internal hierarchical linking structure to optimise the flow of link juice. This has been written about before, in the context of tag clouds and of breadcrumb navigation. But there’s another way to optimise to your internal linking structure: selectively “nofollowing” some of your internal links. Google engineer Matt Cutts refers to this tactic as “sculpting your PageRank.”
Rel=nofollow (which can be inserted into the HTML of the link like so: <a rel=nofollow href=”wherever”>) was originally developed by the search engines to remove the incentive for blog comment spamming, and the search engines positioned the nofollow as a way to not “vouch” for a link (i.e. to not treat it as a “vote” that passes link juice). But the engines have evolved their thinking and developed their algorithms. They have now realised that rel=nofollow is a much more versatile tool than first conceived. Matt Cutts was quoted recently as saying:
“The nofollow attribute is just a mechanism that gives webmasters the ability to modify PageRank flow at link-level granularity. Plenty of other mechanisms would also work (e.g. a link through a page that is robot.txt’Ed out), but nofollow on individual links is simpler for some folks to use. There’s no stigma to using nofollow, even on your own internal links; for Google, nofollow’ed links are dropped out of our link graph; we don’t even use such links for discovery. By the way, the nofollow Meta tag does that same thing, but at a page level.”
Speaking of anchor text, it brings to mind another use for nofollows on internal links: when the anchor text is suboptimal and the link is redundant. For example, I’ve seen countless blogs with multiple links to the same permalink page: one uses the post title as the anchor text, and the others contain such throwaway anchor text as “Continue Reading,” “Comments,” or “Permalink.” On ecommerce sites, you’ll see this same phenomenon manifest itself as redundant links leading to product pages: one uses the product name, the other uses throwaway phrases like “Click Here” or “Order Now” or “Product Info” or the product’s price; or the link is an image of the product with an alt attribute of “product image.”
The first place to begin sculpting PageRank is on your home page, because that page holds the most weight. Typically, the home page needs fewer links to new or recently-reviewed products, and more to top-selling (and high margin) products. Often, you see that a retailer’s home page has well over Google’s recommended “100 links per page.” In an interview with Matt, he offered further insight into Google’s “100 links” guideline:
“The reason for the 100 links per page guideline is because we used to crawl only about the first 101 kilobytes of a page. If somebody had a lot more than a hundred links, then it was a little more likely that after we truncated the page at a 100 kilobytes, that page would get truncated and some of the links would not be followed or would not be counted. Nowadays, I forget exactly how much we crawl and index and save, but I think it is at least, we are willing to save half a megabyte from each page. So, if you look at the guidelines, we have two sets of guidelines on one page. We have: quality guidelines which are essentially spam and how to avoid spam; and we have technical guidelines. The technical guidelines are more like best practices. So, the 100 links is more like a “best practice” suggestion, because if you keep it under 100, you are guaranteed you are never get truncated.”
To get some insight into how some of the bigger online retailers were sculpting PageRank, if you look through Internet Retailer magazine’s “Hot 100″ Retail Websites using the SEO for Firefox extension, which highlights nofollowed links in red you will find that hardly any of them employed “nofollows” on their home page to sculpt PageRank. This is therefore a huge opportunity for the retail industry amongst many others to take advantage of this knowledge.
So, what are you waiting for? Get sculpting!