Matt Cutts answered yesterday a rather unusual question: “Can nofollow links hurt my site?” By logic, Cutts said that whether these links have been built in order to publicize the website and not for the sole purpose of mass linkbuilding, there is no problem and Google could not decide to undertake manual spam action to penalize.

Matt Cutts
 

The head of the Webspam Team at Google explained it in the following video wearing a Firefox shirt while his employer is the owner of rival browser Chrome:

If we remember, Matt Cutts, days ago, has released a series of seven videos that explain the circumstances under which Google applies manual penalties on websites. These videos will help those who received manual penalties via their console Google Webmasters Tools.

Unnatural links from your site:

Unnatural links to your site:

Unnatural links to site – “Impact Links”

Little content or content with no added value:

Hidden text and/or Keyword Stuffing:

Pure spam:

Spam generated by users (eg forums):