Google’s Supplemental Index
What is the Google Supplemental Index?
Google has two indexes - the main Google index and the Google Supplemental Index. The easiest way to describe the difference is that the pages that the Google spiders rate as currently relevant go into the main index, the pages that are read as having little relevance, go into the supplemental index. There are other pages which are read by the spiders as having no relevance and they don’t find their way into either Google index, so the supplemental index at least signifies that a page has some relevance, so all is not lost if your pages find their way into the supplementals.
The supplemental index is only used as backup by the main index. It is rare for supplemental results ever be used when someone searches a specific term, unless that term is so unique that there are no pages in the main Google index that is found to be relevant for that term.
For example, I have just chosen a completely random keyphrase, windburn blue in chichester and although Google have only pulled up 1 result, the algorithm doesn’t see fit to pull anything from the supplemental index, despite the fact that there are hundreds of thousands of supplemental pages with blue and/or chichester on the page. (Although, it has to be said, that by the time this is cached, it’s likely that there will be two results for that term - including this page!) I use this example to show that if your page is listed in the supplementals, you would just as well not have it listed in the the index at all.
Tomorrow, I’ll explain how you can find out which of your pages are in Google’s supplemental index and the various reasons for the pages going supplemental, rather than earning a place in the main index.