‘Supplemental results’ refer to web pages that are not given as much weight by Google as other web pages for the specified term for which they are indexed. As a result, these web pages are deemed of lesser value by Google and are stored in a ‘supplemental index.’ They are only included in the primary search engine results pages (SERPs) if there are no other web pages from Google’s primary index that match the query.
There are several reasons Google may not consider your web pages worthy of the primary Google search index. Some of the reasons may include: your web pages do not have sufficient relevant ‘inbound links;’ they contain duplicate content; they have too many reciprocal links and not enough ‘one way’ ‘inbound links;’ your ‘inbound links’ are not quality links; or your content isn’t dense enough.
If you already have a great number of your web pages in the ‘supplemental index’ then an analysis will have to be done to determine how the situation may be rectified. Comprehensive search engine optimization is always a good idea to ensure your web pages contain what they need to be recognized both by the search engines and your target audience groups as offering value.
