The Google Disavow Links Tool: Summary of Objective and Use
http://bit.ly/1i0DEbM The Disavow Links Tool was released by Google in October. Its purpose is to enable you to identify low quality links and request that Google does not take such links into account when calculating your PageRank. You can therefore reduce the effect of link spam or irrelevant links on your web pages.
What Links Can Harm Your Page Ranking?
Google lists web pages, not entire domains or websites. However, while each page is fundamentally indexed and listed on its own merits, your entire domain could suffer if you are using low quality links on numerous pages. What is a low quality link? Here are some examples:
Paid links: you have paid for backlinks to be generated by a third party.
Irrelevant links: links from pages that have no relevance to your target page content.
Reciprocal links: Excessive link exchanges - some may be acceptable, but only Google knows what is 'excessive.' This is often associated with the irrelevant links mentioned above.
Low Quality Articles: Links from poorly written articles. If you pay a small amount for a large number of articles they are likely badly written. This will harm your ranking.
Comment Spam: Software-generated comments on other people's blogs.
Web Spam: Links from web spammer sites
Automated Links: Software generated links or automated programs that create links.
Contextual Links: You often see these in blue on passages of online text. The links appear to be irrelevant to the topic of the page. These are software generated and can result in your PageRank being reduced and your listing being harmed if they are linked to your website.
Keep in mind that we are discussing links to your web pages. Links from your web pages to spammy sites will also harm your ranking, but you can remove these manually yourself. You cannot remove links published on other websites (more on this below).