Disavow (v): To deny any responsibility or support for something. This definition succinctly describes Google's Disavow Links Tool, which allows webmasters to disavow links to their websites if they feel that the links are causing harm. If ever there was a time to say, "With great power comes great responsibility," this is it.
At the Pubcon keynote today, Google's Matt Cutts announced that the Google Disavow Links tool is now available while stressing that webmasters need to be careful when using it. Said Cutts, "Most sites shouldn't use this tool. Use Caution. Don't just start disavowing links. Please start slow." The tool has been in beta for the last few weeks.
The Disavow tool is most beneficial for webmasters who have received notice of a manual spam action caused by unnatural links to their website. Using the disavow tool, Google can be instructed to ignore these links when evaluating your website. According to the Google announcement, if you haven't received a notice of spam action caused by unnatural links, you've little use for the tool.
In order to use the tool, you'll need to visit the Disavow Tool link and select your website. If your website isn't verified, you'll need to verify it before continuing. Once verified, you'll then be prompted to upload a plain text file containing the links you want to disavow, with one link per line. Once the file is submitted, the links will be disavowed, for better or for worse.
[via Google Webmaster Central Blog]