Google defines supplemental results as follows:
“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.”
If your web pages are listed in the supplemental results then it is likely that your web pages could not be parsed correctly by Google’s standard crawler.
The problem with Google’s supplemental results are that they are only supplemental. If your web pages are listed in the supplemental results then they won’t be returned very often for regular search queries.
How to find out if your web pages are in the supplemental results
An easy way to find out how many of your pages are listed in Google’s supplemental results is to search for the following on Google.com:
site:www.domain.com ***
Search for that phrase and then proceed to the last result pages to find the supplemental results. Of course, you have to replace www.domain.com with your own domain name.
How to get out of Google’s supplemental results
Most web sites have pages in Google’s supplemental results. It means that Google had difficulty to index these pages or that Google had other problems with these pages.
1. Make sure that your web pages don’t contain any spam elements and that you don’t use any spam techniques to promote your web site. Using spam techniques to promote your web site is often the reason why a web site doesn’t get good rankings. Better focus on ethical search engine optimization methods.
2. Make it easy for search engines to index your web pages. If possible don’t use web page URLs that contain question marks or the & symbol. Make sure that the HTML code of your web pages offers what search engines need. Use IBP’s Top 10 Optimizer to prepare your web pages.
3. Make these pages easy to find for Google’s web crawler. The more links point to your web pages, the more likely it is that search engine crawlers fill find your web pages. Use ARELIS to get good inbound links to your site.
Most web sites have pages in Google’s supplemental results. The easier you make it Google to index your web pages the more pages of your site will be listed in Google’s normal results.