Google Panda Refresh Version 21
Notice a minor change in your Google rankings/results the past few days? Yes, another Panda Update occurred on Monday affecting, according to the search engine, only 1.1% of U.S. English queries, titled Google Panda Refresh Version 21. The previous update occurred not too long ago on September 27th and affected 2.4% of English queries, and was also a Panda algorithm change, rather than a data update.
This follows the approximate every four to six week release schedule of each update made by Google, which claims search algorithm changes are made up to 600 times annually on the minor scale. But, sometimes these algorithmic updates can be major for high ranking websites.
So, for SEO, it does help to now understand approximately when these updates will be made – next one scheduled for Google maybe the beginning of December or mid-month? This might help in the explanation to some clients with changes in rankings and web traffic. However, some websites seem to escape the hits from Google, if and only if SEO has been performed properly.