Google Panda is one of the major update that affected the ranking of numerous websites on search result pages. All those who have been penalized should make the needed changes, after a thorough analysis to improve upon the ranking.
Google keeps on launching new updates in order to help searchers to the extent possible. One of the recent updates that hit numerous sites is Google Panda update. It encouraged sites with high quality content, while at the same time, penalized poor quality sites that gained top ranking. These sites were those that have low-value add for users or have copied content, whereas the sites with original and informative content with in-depth reports and thoughtful analysis gained good ranking. In order to save sites from “collateral damage”, Google asked high quality sites that have been negatively affected to let them know it.
In order to define low quality site, Google would have considered various factors, such as low quality or duplicated content, high amount of irrelevant adverts, over optimization, irrelevant page content, high bounce rate, low visit time, low quality inbound links to a site, low click-through-rates, etc.
Panda can said to be an algo change that works like penalty. The results of an algo change can be regained, once the change is made. However, it affects the whole site. Panda updates hit different pages of the site to different extent. Likewise, panda also affected the sites at different keyword level.