Being dumped by Google? Learn how to avoid becoming a victim next time around! (Part 2)
Periodically Google make changes in order to stop some webmasters to get unfair advantages by plugging one or two of the loopholes.
This is what happened during the Florida update.
With this update Google introduced new algorithms which intended to stop overuse of some search engine optimization techniques.
More specifically they seem to have targeted search terms found in text links also called anchor text. Web pages with good positions in the search result, which had had a disproportional number of in-bound links to them from other web pages with the exact same search term in the anchor text that the page was optimized for suddenly, disappeared from the listings.
The pages did not disappear altogether. Just for the search term that the page were optimized for.
For Google, the high proportions of anchor texts with the same text indicate that the texts were put there for one purpose only, to boost ranking.