econman - 7:48 pm on Mar 4, 2011 (gmt 0)
This is an article I have published on a "content farm" that got hit.
It sounds like this might be an example of a page dropping in the SERPs not because of its own characteristics, but because it is located on a site that has numerous other pages (or a high proportion of other pages) that have been scored as poor quality.
If so, it isn't clear why this ripple effect is taking place. I see two basic possibilities:
Perhaps all pages on a "low quality" site are being demoted -- some sort of site-wide ranking change which is adversely impacting your page.
Or, numerous low quality pages on the hosting site are now being devalued by Google when it does all of its internal link juice calculations. In other words, perhaps your page was previously benefiting from being located on a huge site, and now it no longer gains that benefit. This wouldn't have to be a huge shift -- even a small shift in the ranking algorithms could be sufficient to push your page down several notches in the SERPs.