We work hard to return the most relevant results for every search we conduct. To that end, we encourage site managers to make their content straightforward and easily understood by users and search engines alike. Unfortunately, not all websites have users' best interests at heart. Some site owners attempt to "buy PageRank™" in the form of paid links to their sites. Buying links to improve PageRank violates our quality guidelines. 
Google uses a number of methods to detect paid links, including algorithmic techniques. We also welcome information from our users. If you know of a site that buys or sells links, please tell us by filling out the fields below. We'll investigate your submissions, and we'll use your data to improve our algorithmic detection of paid links.