Although Bing beat them to it some time ago, today Google announced their new Disavow Links Tool. It’s a way to help you tell Google if you feel some of the links pointing to your website could be hurting it in the search results.
If you’ve either been done some very questionable linking to your website or your SEO company has, then you may find that your website has been somehow penalised for this in search results.
Alternatively, it could be that one of your competitors has pointed a load of spam links to your site, either way, it’s not too difficult to bring a website crashing and burning down.
In a way this new tool is Google’s admission that other websites can harm your rankings, even if it’s no fault of your own.
Unless you have serious problems with your website’s rankings and received an unnatural link warning in Webmaster Tools, or you’ve been hit by that unfriendly Penguin update, then you don’t need to use this at all.
It’s sometimes difficult to know which links to you site are actually causing it problems, so unless you really know what you’re doing, don’t use it.
It takes weeks for Google to ignore the links you tell them about and even longer if you are trying to reverse it.
Here’s Matt Cutts saying what you need to know about all of this: