Google has refreshed 25th Panda update on 20 February, 2013. Google refresh Panda update in less than one month of 24th Panda update on 22 January, 2013 that affected 1.3% search queries.
Google Panda is a change to Google's search results ranking algorithm that was first released in Feb. 2011. The change aimed to lower the rank of "low-quality sites" or "thin sites", and return higher-quality sites near the top of the search results.