There is always a bit of a paddy when Google changes the index. Of course in truth they are constantly tweaking both the way they index and the page layouts, some say they are changing at least weekly, and probably much more often than that.
But Panda was something a bit more
Having said that, the recent change labelled 'Panda' by most (and 'Farmer' by some) does seem to have made some sites very unhappy indeed. Panda started in the US in February and was rolled out to the UK in April 2011 and the changes were quite dramatic for some. Google, quite unusually even got into a discussion publically about what the intention of the change was. The idea, according to Google, was to reduce the prominence in the listings of "low quality" sites, especially those that were primarily duplicate content, often with ads wrapped round them. Panda is like a filter to analyse and score sites and pages and then use the result to filter out, or handicap, sites that appear not to add to the objective of high quality, relevant results.
Some sites reportedly lost up to 88% of their traffic, and it hit affiliate sites particularly hard. Having said that, some sites that obviously felt that they should have been affected were quick to publically state that there were not, such as discountvouchers.co.uk.
And you ain't seen nothing yet
There is some expectation that Panda 2.2 is just around the corner, so once again sites and SEO companies are bracing themselves for some head scratching and unhappy customers. This filter can be expected to experience further tweaks and the data will also be being updated not in real time but in batch updates - some think every 3-4 weeks. As new tools and indicators become available to Google, such as Google +1, then it is logical that they will look at whether they can be used as a market to enhance the quality measures.
So, what to do if Google Panda gives your site a black eye
Firstly you need to know that you have been impacted at all, and for that you need to be running analytics on your site. Google analytics is the one we normally recommend and is free, but there are others. Study the Google organic traffic and see if your traffic dropped during April, and whether it has climbed back up since. One of our consumer sites with adsense revenue actually went up, but then again it has unique content and so is the type of site that might be expected to benefit. It is a very small site but shows that the effects are not all one way. In the first week of April it got 498 visitors from Google, non-paid traffic, and by the first week of May this had increased to 709, so a useful increase of 40%.
On the other hand we have heard of sites like hotel brokers and travel sites where there will often be a common hotel description being used across hundreds of sites where traffic fell. The lesson here is that if you are the hotel make sure your own sites use a different description than is given out to affiliates. If you are an affiliate, then consider how you can reformat and enhance the descriptions you are given.
So what should a site do? In reality, common sense normally prevails (except if you are talking about Google Places but that is another story), and sites that do the basics well and for the right reasons (for users rather than for search engines) usually have nothing to fear. Over optimisation of your site, setting up duplicate gateway pages and using doubtful link building and directory submission systems can all start to show a trail of search engine abusive behaviour that is just waiting to be slapped down, either by Panda and whatever it evolves into.