New anti-spam tag

The new nofollow tag is designed to stop spammers from entering links in blog tool comments fields.

(January 20 2005, update January 22) In an attempt to stop spammers from unduly influencing search engine results, several search engine companies, including Yahoo!, MSN, and Google have joined rank to add a new tag to the HTML vocabulary.

Blog comment spamming

The story goes like this: Creative webmasters are constantly developing new ways of improving their search engine positions.

Given that the number of incoming links to any web page will influence its ranking (the search engines see links as a mark of quality), many webmasters try to get as many links as possible.

One way of doing this is to add comments to the large number of web logs appearing all over the web. These web logs are often generated by software that leaves room for such comments. These webmasters will, of course, include a link to their own site.

The nofollow tag

A large number of blog software makers have now decided to add this tag to their software, meaning that the software will automatically add the text rel="nofollow" to any link tag in the comment fields.

As Google put it:

"So if a blog spammer previously added a comment like
Visit my <a href="http://www.example.com/">discount pharmaceuticals</a> site.
That comment would be transformed to
Visit my <a href="http://www.example.com/" rel="nofollow">discount pharmaceuticals</a> site."

The search engines will then not use these links to calculate page rank., nor will the search engine spider follow the link to the next page.

Google and other search engine make use of the anchor text, i.e. the clickable text, to decide what the page the link is pointing to is about. If there is a nofollow-tag, the search engines will ignore this text.

No punishment

The sites that receives such links will not be "punished" for them, i.e. their ranking will not be reduced by them. Moreover, such pages can be indexed if the search engine can find them by the way of regular links.

Link exchange cheating

One more thing: Webmasters that exchange links with other webmasters, should take a close look at the relevant link code.

Some could be tempted to include a nofollow tag in order to avoid "losing" page rank. That would render the incoming link useless from a search engine optimization point of view.

The new tag is, according to Google, supported by blog tools like LiveJournal, Scripting News, Six Apart, Blogger, WordPress, Flickr, Buzznet, blojsom, Blosxom and MSN Spaces

Working Together Against Blog Spam (MSN Search Blog)
A Defense Against Comment Spam (Yahoo! Search Blog)
Preventing comment spam (Google Blog)
Support for NOFOLLOW (Six Log)
Webmaster World discussion

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