Bill Slawski covers the 20 different ways search engines may rerank search results. It’s certainly worthy of a read.

Here’s a summary of the main points:

  1. Filtering of duplicate, or near duplicate, content
  2. Removing multiple relevant pages from the same site
  3. Based upon personal interests
  4. Reranking based upon local inter-connectivity
  5. Sorting for country specific results
  6. Sorting for language specific results
  7. Looking at population or audience segmentation information
  8. Reranking based upon historical data
  9. Reordering based upon topic familiarity
  10. Changing orders based upon commercial intent
  11. Reranking and removing results based upon mobile device friendliness
  12. Reranking based upon accessibility
  13. Reranking based upon editorial content
  14. Reranking based upon additional terms (boosting) and comparing text similarity
  15. Reordering based upon implicit feedback from user activities and click-throughs
  16. Reranking based upon community endorsement
  17. Reranking based upon information redundancy
  18. Reranking based upon storylines
  19. Reranking by looking at blogs, news, and web pages as infectious disease
  20. Reranking based upon conceptually related information including time-based and use-based factors

There’s been talk lately in various forums that Google in particular places sites with minor infractions on the 4th search result page. Statistics show that any results on the 4th page onwards get little to no traffic. This phenomenon is also referred to as the -30 penalty. No one knows for sure if this is permanent (if not, penalized for how long) and to what degree the infraction would cause something like this to happen. I personally haven’t seen downward changes in my client’s sites movement. Those who have sites in the top 10 suddenly drop to the fourth page would do well to investigate possible problems like links from bad neighborhoods, appearance of purchased links, lack of unique content, etc.