learnseo81 - 2:05 pm on May 20, 2011 (gmt 0)
This is EXACTLY what happened to me on May 13. When did this happen to your sites?
My all terms are buried in deep pages like page 4, page 5, page 6 and my SERPs are bouncing like a yo-you. Rank for my pages get +25 and -27. I was #1 for all those terms. Top 10 results are changing every minute I refresh the page.
95% of my terms have dropped or say 100%. Overnight. I've 70 pages of unique 1000 words content targeting several long tails and all SERPs are nowhere to be found.
It is not happening with you alone. Can you check If your SERPs are also bouncing wildly? Also monitor the top 10 results and let me know If those results are changing.
Its SITEWIDE Drop!
One thing, according to me, your sites which have dropped should be in the similar or same niche.
I believe google is testing out some SPECIFIC niches and DOMAINS at the moment.