Robert_Charlton - 8:55 pm on Jan 22, 2013 (gmt 0)

A Googler @google New Panda data refresh rolling out today: 1.2% of English queries affected. Background: http://goo.gl/8Zqy1 [goo.gl]

Regarding the Background link in the twitter post (not to be confused with the link to the twitter post...

Yes, it's a genuine announcement. The link refers to the original history.

It's worth noting in all these updates that Google is continuing to link back to the May 6, 2011 Google Blog article by Amit Singhal on the kinds of signs which Google is considering when determining quality....

More guidance on building high-quality sites
[googlewebmastercentral.blogspot.com...]

This should be taken as a big clue. Here is a group of the kinds of questions that Google looks at. These four in particular, grouped together toward the end of the list, struck me as particularly important to think about when you evaluate your content quality...

- Would you recognize this site as an authoritative source when mentioned by name? - Does this article provide a complete or comprehensive description of the topic? - Does this article contain insightful analysis or interesting information that is beyond obvious? - Is this the sort of page you’d want to bookmark, share with a friend, or recommend?

Questions along these lines are then used to choose and evaluate sets of seed pages... and trial and error based algorithms (aka heuristic algorithms)... which are tested, refined... first, as I understand it, in the original seed set, then in a wider sample of pages, and finally incorporated into the larger Google algorithm.