Over the past few months we have covered a few issues and tips relating to Google's supplemental index.

For those of you that are unaware, Google essentially maintains two databases for its search results.  The "main index" in which it places pages that it believes are of a "premium quality" (my words, not Google's) and the "supplemental index" in which it would place everything that may be considered "peripheral" or dare I say - "supplemental". 

Despite Google's previous attempts to reassure people to the contrary, content in the supplemental index was crawled/updated less frequently and would be considered to have a lower weighting than that in the "main index" (i.e. supplemental results did not perform in the search engine results pages as well as those from the main index). 

These results were flagged in the search engine results pages (SERPs) with a "Supplemental Result" text next to it. Google announced last week on their official blog that these results will no longer be flagged with this text.

One of the reasons that they give is that results from the supplemental index are now included in the SERPs as frequently as those from the "main index" and they don't want to imply that the result is flawed in anyway.  I suspect that the universal search algorithms have something to do with this as the new search results will combine results from images, videos, blogs and news - and so it would not take a huge leap to consider that they can pull and rank web content from two different indexes as well.

Knowing that pages were supplemental was useful for seo companies as it highlighted pages that had issues with indexing, duplicate content, and back-links (to name a few).  

There is a suggestion that information relating to the supplemental index will be moved to the webmaster control panel so that the usefulness will not be lost on those who need it which sounds like a good idea to me.