As I have said before, we have a 1000+ page website, all original, useful content. In fact our content is so useful several Wikipedia pages are stolen from us verbatim. We have never asked for a link or paid for a link, so all our external links are 100% legitimate. Up to February 2011 we were at the top of every search we cared about, and whenever we put up a new page it would be on top within 24 hours. Life was good. Then came the first famous Panda attack when we lost about 20% of our traffic.
Since then the pattern is that we move up gradually until the next update and then get hit another 20%. We are now 40% of our original traffic, which is very sad because we never did any of the bad stuff and now spammy sites outrank us everywhere.
Of course I started working like crazy to overcome the penguin and panda penalties, here is a short, incomplete summary of what we did since February 2011. None of this was effective:
Took out a lot of internal links
Started advertising using Google adwords
Changed the site from Frames to CSS
Most of the site was converted to HTML the exception is the shopping cart
Searched for sites that stole our content and either shut them down or changed our content
Added Geosite sitemap.
Worked on branding by adding our site to some better directories and also advertising on linkedin and ebay
Reworked all the graphics and optimized the size of the images
Shortened the average load time by a factor of 5
All our pages now have >92% score on “page speed”
Tightened up the content, removed a lot of fluffiness, tried to eliminate duplicate text in product descriptions of similar products
Tightened up the site maps
Used robots.txt to remove irrelevant pages from the index, such as the shopping cart links
Submitted properly formated and rigorously scrubbed site maps
Cleaned up all the duplicate meta descriptions reported by Webmaster Tools
Cleaned up all the short meta descriptions reported by Webmaster Tools
Added authorship verification to try to keep our original content identified
A PR7 web site references one of our pages 20,000 times with the same anchor text, I removed them, as well as some of the more idiotic forum links (the same text repeated ad nauseum).