My SEO e-Guide by Nicolas Gremion - HTML preview

9. Ranking History

Google will look at the historical ranking of a document to help determine the current ranking. A historically highly ranked document will have an influence on the current ranking. A document that falls significantly in rank would be flagged as 'out of favor' and may be considered outdated.

• A document that jumps in ranking across a number of queries might be a topical document or could be SPAM. Commercial queries can be repeated and documents that are ranked highly can be nagged and checked for SPAM. The change in rank over time is considered to see if a document is SPAM. If there is a sudden spike and the document is not linked to or from an authoritative or trusted source, like a news article, then a document may be considered as SPAM.
• Try to get links from trusted news and authoritative sites.