The random surfer may not have noticed that the supplemental index tag has been dropped the webmaster and SEO communities sure have. On July 31st 2007 a post on Google’s Webmaster Blog announced the change. It is still possible to see which of your pages are in the supplemental index by performing a search for site:yoursite.com/& on Google. I’m very interested to see if this means of “seeing” your supplemental pages gets eliminated in the near future.

What I find most interesting from the official announcement is this…

We’re also working towards showing more Supplemental Results by ensuring that every query is able to search the supplemental index, and expect to roll this out over the course of the summer.

This will be a drastic departure from the way Google has produced search results. Instead of looking into the regular index first and only moving onto the supplemental index only if they cannot find enough good matches there, they are going to have to implement a new threshold if indeed they want to “ensure” all queries reach the supplemental index.

While I can certainly see where exact phrase matches or titles be used to help this happen with multiple word queries, what about very popular two word queries or single word searches? A search for SEO as an example, would likely never make it to the supplemental index unless they develop a very specific stopping point at which they automatically looked into the supplemental index. What if that stopping point was a specific number of pages?

If we suppose that the data set that is built for a query is still around 40K pages, then one possibility would be to automatically stop looking in the regular index for matches at a predefined number and then move onto the supplemental index to finish filling the data set with the best matches from there. Naturally, they would have to start, if they already haven’t, fully parsing and indexing the pages that are in the supplemental index for something like this to have any real effect. This would give pages in the supplemental index a fair chance at being ranked.

Will all queries reach the supplemental index in 2007 or shortly after? I certainly hope so. The supplemental index is simply not what it used to be and it contains plenty of fine pages that deserve the opportunity to be found and seen by the random surfer. Time will tell if this is merely wishful thinking or a true departure from what was, to something that should definitely improve the quality of Google’s search results.

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