The types of websites that have been affected by Panda are sites with:
Thin content: Little original content or little content but websites full of advertisements and links. These are sometimes known as content farms
Duplicate pages to target keywords: Duplicate content is a big no-no in 2013 for SEO. It used to be a tactic to create multiple versions of the same page and target different keywords. So you may be based in the south of England and you have a page for each different county. Too much duplicate content is now being penalised
High ad ratio: A website with more ads than actual content, and especially ads above the fold
Empty web pages: This usually isn’t something intentional but fusion database happens on websites. This could be empty pages from search functionality for example. Housekeeping and tidying up your website regularly should prevent this
Purchased links: We all know link building is a major SEO tactic, however natural link building is the tactic, not buying lots of links from websites that sell them
How to recover from or prevent further issues from your website
Let’s go back to basics and understand what search engines (especially Google) want:
When a search takes place Google tries to match the keywords searched for and rank relevant websites
Search engines like unique, fresh and engaging content that is written for humans (not search engine robots)
Search engines like trusted and authoritative websites. This is usually measured by links back to a website with each link from another site being a ‘vote’ in Google’s eyes for your site. The more authoritative the website that link comes from the better, so a link from the BBC is worth more than a brand new website. The view is if you have great content other sites will link to it
The major premise of recent search engine updates are about a focus on fresh and unique content and clamping down on dubious tactics. Create quality content, build links but build good links and make sure if you have a site or use the tactics that the Panda updates are targeting that you change them quickly.