How to Get Out of the Google Supplemental Index Hell
First things first – lets define the Supplemental Index. The best way is to take it straight from Google
A supplemental result is just like a regular web result, except that its pulled from our supplemental index. Were 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 youre a webmaster, please note that the index in which a site is included is completely automated; theres 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 doesnt affect its PageRank. For tips on maintaining a crawler-friendly site, please visit our webmaster guidelines.
Reference: Googles Webmaster Help Center
