A supplemental result is a URL residing in Google's supplemental index, a secondary database containing pages of less importance, as measured primarily by Google's PageRank algorithm.
Contents
- Duplicate Content
- Low PageRank
- Lack of Trust
- High Page Count
- Page Freshness
- Recommended Solutions to Supplemental Results
- References
The importance of a page is measured by the number and quality of links pointing at it. The degree to which Google trusts a site's inbound links also influences the importance of a page. If Google detects paid links, for example, it will devalue the links or nullify them completely so that PageRank will not pass to the target page.
A supplemental page will still rank in search results, but only if there are not enough pages in the main index that are returned within the search.
Google used to place a "Supplemental result" label at the bottom of a search result to indicate that it is in the supplemental index; however in July 2007 they discontinued this practice and it is no longer possible to tell whether a result is in the supplemental index or the main one.[1] [2].
Duplicate Content
Some people believe that the supplemental index is Google’s way of filtering out duplicate content. TITLE elements, META descriptions tags, and navigational text that are similar or identical can lead to duplicate or near-duplicate content.
Low PageRank
However, duplicate content is a side effect of supplemental results, not the cause. Instead, low PageRank is the primary cause of supplemental results. Links to multiple versions of the same page dilutes PageRank across multiple URLs, thus increasing their chance of not reaching a minimum PageRank threshold. If a page's PageRank is too low, Google will drop it from its main index. That page will appear in search results as a supplemental result.
Lack of Trust
Manipulative linking practices can also lower PageRank flow into a domain, thus creating more supplemental pages. Manipulative links include excessive reciprocal linking, link injections, and paid links. Questionable outlinks can also lead to link devaluation.
High Page Count
A large site with a high page count is also generally more vulnerable to the supplemental index than a small site because inbound PageRanks divided among several hundred thousand pages tend to be lower than that divided up among only a few dozen pages.
Page Freshness
Page freshness is also a factor.
Recommended Solutions to Supplemental Results
The primary cure for supplemental results is more quality backlinks. Other solutions include internal links restructuring and trust management.