Forbes recently wrote an article about Google's supplemental results, painting it as webpage hell. The article states that pages in Google's Supplemental index is trusted less than pages in the regular index:
Google's programmers appear to have created the supplemental index with the best intentions. It's designed to lighten the workload of Google's "spider," the algorithm that constantly combs and categorizes the Web's pages. Google uses the index as a holding pen for pages it deems to be of low quality or designed to appear artificially high in search results.
I have worked on some of the largest sites and network of sites on the web (hundreds of millions+ pages). When looking for duplicate content or information architecture related issues, the search engines do not allow you to view deep enough to see all indexing problems, so one of the first things I do is use this search to find low quality pages (ie: things that suck PageRank and do not add much unique content to their site). After you find some of the major issues you can dig deeper by filtering out some of the core issues that showed up on your first supplemental searches. For example, here are threadwatch.org supplemental results that do not contain the word node in the URL.
If you have duplicate content issues, at best you are splitting your PageRank, but you might also affect your crawl priorities. If Google thinks 90% of a site is garbage (or not worth trusting much) I am willing to bet that they also trust anything else on that domain a bit less than they otherwise would, and are more restrictive with their willingness to crawl the rest of the site. As noted in Wasting Link Authority on Ineffective Internal Link Structure, ShoeMoney increased his search traffic 1400% after blocking some of his supplemental pages.
Gain a Competitive Advantage Today
Your top competitors have been investing into their marketing strategy for years.
Now you can know exactly where they rank, pick off their best keywords, and track new opportunities as they emerge.
Explore the ranking profile of your competitors in Google and Bing today using SEMrush.
Enter a competing URL below to quickly gain access to their organic & paid search performance history - for free.
See where they rank & beat them!
- Comprehensive competitive data: research performance across organic search, AdWords, Bing ads, video, display ads, and more.
- Compare Across Channels: use someone's AdWords strategy to drive your SEO growth, or use their SEO strategy to invest in paid search.
- Global footprint: Tracks Google results for 120+ million keywords in many languages across 28 markets
- Historical data: since 2009, before Panda and Penguin existed, so you can look for historical penalties and other potential ranking issues.
- Risk-free: Free trial & low price.