Google rankings up and down...

[axum]

Can anybody explain why does the google rankings change so often and sometimes very dramatically?
an example: with search criteria "costa blanca" the http://www.info-costablanca.com usually appears on the first 2 pages, but then sometimes it is totally gone to pages 34 or more...?

Thanks for any explanation

Axum

[awall19]

they are playing with filter setting (I believe)

they implemented a spam filter and are using some sort of reranking algorithm on certain terms (those which have enough of an authoritative community behind them to institute the rerankings)

http://www.search-marketing.info/newsletter/articles/google-continued.htm