What are possible causes of a sudden drop in google serps for some (not all) queries?

Question

A site I manage has seen a sudden drop in visits from google.

It used to have about 300-500 daily visits until a week ago. They were 10% from a strong, competitive query; 80% were long tail queries. Now I lost both, and visits dropped by 90%. I still have

There were no changes on the site for the last 3 months, and all changes since last year were trivial. I din't notice any PR changes lately.

What are possible causes of this?

I assume I wasn't banned, as I still have a couple of top ranking queries.

[edit] My pagerank didn't (apparently) change. I still have 4 in the homepage.

Answer 1

Google dance A phenomenon in which the search results returned by Google appear to fluctuate and change. This is a result of inconsistencies among the different Google data centers as they each undergo updates to their individual indexes. The term Google dance is an unofficial term.

From http://www.harvestseo.com/seo-glossary-g.html

See also Google Everflux

Answer 2

I don't believe "Google dance" explains observed behavior: the indices do get updated in individual data centers separately, but once the update is finished (which takes less than a day, as far as I understand), you should expect consistent search results regardless of which of the Google data centers was hit.

The OP didn't say which site "suffered".

Maybe some human at Google looked at it and decided that it should be penalized for (spam, malware, MFA, or whatever)? Or there could now be new sites which "answer" both queries better.

Answer 3

This is not google dance. We're experiencing the same thing. We went from first page to - non existant! Mostly on geographical search terms... But a few others are still ranked highly.