It is an updation on Google algorithm which is more focusing on high quality content, so search engine can provide quality content to user rather than low quality content.
to remove the spammy website form the top of the search engines google just introduced the new structure of algorithm is called google panda effect..
google has been renewing the algorithm, the change is very quick, recently website including and the place changed express, the place might use the real-time renewal to analogy
I will tell you what Google Panda is for real. It's like a lottery, they make a draw every 3 to 6 weeks and if your website is on the list, that's it "Game Over", They don't really care that your site is Spammy or not, my sites were ranking very well for more than 3 years (imagine Google was doing it all wrong for 3 years, and now they figured how it should be), now it lost about 70% of traffic. You can call Google Panda anything you want, but don't tell me it does improve search results or filters spam!
All I know is its hard to think that Google will do something that actually makes search results less targeted to the search terms. That is the whole purpose and they are pretty smart so its safe to assume their change will be for the best. It may be different/harder to rank sites hard but even as an SEO guy, I think that's good. I only rank up sites that should be at the top anyway so the better Google makes their search engine, the faster my sites will get ranked up as will yours if your not being "spammy" or unnatural.
same happen with my site.... its running good from last 1 year, even after all its updation of panda 1, 2, 2.1, 2.2, 2.3, & 2.4, but suddenly it went down 40% after 2.5 panda update, its true... lottery system i think
Panda update is all about trying to lower spun/low quality articles in the SERP. Unfortunately, Google is not always that accurate... :/
I call it as well the google lottery a new toy by google, as long google doesn't say to the webmasters what's wrong with the sites
As of 24th Feb 2011, a major update by Google on how it ranks sites has affected 12% of search results and halved many sites’ visitor numbers. Named the Farmer or Panda Update it’s only affecting US Google results as I write but if you’re outside the US it is coming to you soon. Here’s how to find out if you have already been hit, are going to be and what to do about it.