  Links are an important signal in our PageRank calculations, as
they tend to indicate when someone has found a page useful.
Links that are purchased are great for advertising and traffic
purposes, but aren't useful for PageRank calculations. Buying or
selling links to manipulate results and deceive search engines
violates our guidelines.  Today, in response to your request,
we're providing a paid links reporting form within Webmaster
Tools. To use the form, simply log in and provide information on
the sites buying and selling links for purposes of search engine
manipulation. We'll review each report we get and use this
feedback to improve our algorithms and improve our search
results. in some cases we may also take individual action on
sites.  If you are selling links for advertising purposes, there
are many ways you can designate this, including:   • Adding a
rel="nofollow" attribute to the href tag We value your input and
look forward to continuing to improve our great partnership with
you.