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If that's the timeframe, it's most likely not the recent Farmer Update. I'd guess it's most likely to be a penalty of some kind (manipulative linking practices, cloaking, thin/duplicate/scraped content are the most likely culprits). You might check out these posts for more detail: http://www.seomoz.org/blog/how-to-handle-a-google-penalty-and-an-example-from-the-field-of-real-estate http://www.seomoz.org/blog/pagelevel-algorithmic-penalties-on-the-rise-from-google