What's a Google Supplemental Result?

This is a common question and there's a lot of confusion about exactly what Google considers supplemental and what it means to be in the Google supplemental index. Before I explain what it really means, however, let me show you a quick example of a supplemental result:

See the key phrase in the green text below the match?

To get the official word on what it means, I used Google to search for "supplemental index", which makes sense. The best match is a page written for Webmasters on What's a supplemental result?

It explains that "A supplemental result is just like a regular web result, except that it's pulled from our supplemental index. We're able to place fewer restraints on sites that we crawl for this supplemental index than we do on sites that are crawled for our main index. For example, the number of parameters in a URL might exclude a site from being crawled for inclusion in our main index; however, it could still be crawled and added to our supplemental index. If you're a webmaster, please note that the index in which a site is included is completely automated; there's no way to select or change the index in which a site appears. Please also be assured that the index in which a site is included doesn't affect its PageRank."

Hmm... sounds innocuous enough. Theories in the SEO (search engine optimization) community are all over the place, however, including suggestions that the pages are too old, too new, duplicate content, orphaned pages that don't have inbound links any more, bad navigation, and even pages that are excluded from being indexed due to the presence of a "robots.txt" file. Does any of that make sense to you? :-)

The always authoritative SearchEngineWatch says: "What are supplemental results? At the same time Google posted new size figures, it also unveiled a new, separate index of pages that it will query if it fails to find good matches within its main web index. For obscure or unusual queries, you may see some results appear from this index. They'll be flagged as "Supplemental Result" next to the URL and date that Google shows for the listing."

If we ignore the paranoid ranting of SEO folk (just kidding, sort of) it seems safe to conclude that Google's Supplemental Index is a database of obscure and weird results that are far from regular Web pages, and that if your own pages are getting stuck in the SI it might be time to redesign them or ensure that you have sufficient textual content to have its crawler work properly.

Anyway, that's not your situation so all you need to know is that, probably, the results you were seeing to your search were probably just pointing to weird, unusual Web pages or similar.