Google recently launched an update which aims to clean up their search results. In a post on their webmaster central blog, Another step to reward high-quality sites, Google explained the background to the update and gave examples of the type of things they are targeting.
Google want to combat what is known in the industry as webspam, webpages created solely to boost a websites position in the search engine results pages. One of the examples given by Google is something called spun content, where a single page of content has been used to create large numbers of subtly different web pages. Words are swapped in each version to keep each page unique but, in some cases, to the extent where the content becomes unreadable.
Many people have already been complaining about the new update and many industry experts have been digging into the available data to try and narrow down exactly what the algorithm update is designed to detect. Along with the "spun content" example, Google pointed to keyword stuffing as another spam tactic designed to gain higher search engine results.