Google在Webmaster Tools页面提到：
“Nofollow” provides a way for webmasters to tell search engines “Don’t follow links on this page” or “Don’t follow this specific link.”
What are Google’s policies and some specific examples of nofollow usage?
- Untrusted content
- Paid links
- Crawl prioritization
However, a solid information architecture — intuitive navigation, user- and search-engine-friendly URLs, and so on — is likely to be a far more productive use of resources than focusing on crawl prioritization via nofollowed links.
html5对rel=”nofollow”的解释道：
rel=nofollow “indicates that the link is not endorsed by the original author or publisher of the page, or that the link to the referenced document was included primarily because of a commercial relationship between people affiliated with the two pages.”
综上来看，不管是从搜索引擎爬虫的角度、还是html5对此的重新定义来看，rel=”nofollow”并不是单纯用来屏蔽搜索引擎抓取的。它包含的语义远大于原先的定义。