The job of search engines is to index every site out on the Internet, rank them according to relevance, and be able to return them based on free-form search. When you think about it, that’s a lot of data. When you perform a search, you want to see the most relevant listings first, and the not-so-relevant ones later. One of the ways Google has managed this is through the use of two different indexes – their main index, and their supplemental results index.

When Google crawls your web site, it determines if your site belongs in its primary index, or in the supplemental results index. Triggers that will get you put into the supplemental results index are:

• Current Google PageRank
• Complexity of your page’s URL
• Repetitive text that looks like you are trying to game the system
• Pages with no substantial content
• Pages with redirect links
• Orphaned pages
• Changes to the algorithms that Google uses to rank pages

This means that if your page is in the supplemental index, your results will show up further down on the Search Engine Results Page (SERP), or when there are not enough results from the main index. As your pages change rank, they move from one index to another. This makes sense – as your page becomes more or less relevant, it will move up or down the SERP and move in and out of the main index. The pages in the supplemental index also have less constraints on how they are indexed, increasing the accuracy of the supplemental index.

Google has made some recent changes to the supplemental results index. They have streamlined indexing, increased frequency of indexing, and tweaked the algorithms that differentiate the two indexes. They have also decided to stop labeling URLs as being from the Supplemental Results index.

What this really means is that you can no longer tell whether your page is in the supplemental index, which was how some folks know that their pages needed some help. Some people think this is a good thing (whether a page is in one index or another has no real value), and some people think it is a bad thing (you are removing critical information from the users and the developers). What do you think?

References:

• Google Webmaster Central Blog – Supplemental Goes Mainstream
• Google Supplemental Results Index – A Word To The Wise
• What are Google Supplemental Results?
• SEO Roundtable – Google Hides Supplemental Results Label
• How I escaped Google’s Supplemental Hell