On April 24th 2012 many websites suffered a drop in search engine rankings after Google launched the Penguin algorithm update.  Two weeks on Matt Cutts has suggested that those affected by this update should review his videos "When are penalties lifted" and "Does Google take manual action on webspam?" in order to understand how to clean up their websites and if the website in question will automatically return to it's previous positions or whether a re-inclusion request is required.