Why do sites get trapped in the supplemental index

[sweetashlee]

There are four prime known reasons why web pages get into Google’s supplemental index –

1. Poor link-backs to the page (shows the content is not worth linking to)
2. Zero or very low PageRank (this is a result of point 1 above)
3. Duplicate content (within the site or copied from other websites)
4. No Content (pages with very little or no content)

From Google’s point of view, in all four instances, the pages demonstrate little value addition to its searchers.

[Zerolized]

Erm... anything extra?