Algorithm rolled out: November 1, 2006
Algorithm overview: Overall gist
The year 2006 was marked by supplemental index revisions. The way pages were filtered altered dramatically as a result of this. Even if it appeared to be a matter of a penalty, Google stated that Supplemental Update was not meant to be a penalty.
The more Google discusses the supplemental index algorithm update or the “supplemental” results in Google, the more SEOs seem to be perplexed. This update basically concentrates on and enhances the missing parts of a complete story. So, at the first move, one will get results from the main index, and then the supplemental index will come to play, especially when everything is equal.
Based on forum discussion, it appears that Google is attempting to convey the idea that the supplemental index isn’t harmful to any site. Whereas all experienced SEOs used to label the supplemental index the sign of death in terms of site ranking in Google, some still do.
Algorithm winners & losers:
Pages with not-so-good ranks were impacted by this Supplemental Update. According to Google, pages that are in the supplemental results will be still visible o the users. But the pages lack the required PageRank to be enlisted in the main index of Google. Pages in the supplemental index do not mean they are penalized. It can result in slight changes in traffic that a site was used to receive before the Supplemental Update hit.
The only cure for such a Google algorithm update hit is trying for getting more quality backlinks. When a page starts getting more and more quality backlinks, algorithms will start treating that page as more valuable. Once a page gains the required quality, Google will move it from its supplemental index to the main index.