nofollow is an HTML meta tags (meta) content attribute and link labels (a) of the rel attribute a value that tells the machine (crawler) without tracking the target page, in order to combat blogspam (blog spam message), Google recommends using nofollow, tell No search engine crawlers crawl the target page, and do not need to tell the search engine of the current page Pagerank passed to the target page. But if you're sitemap submitted directly through the page, crawling reptiles still here on this page nofollow target page just an attitude, not on behalf of other pages on the attitude of the target page.

The use of nofollow

nofollow in two ways:

1 for meta meta tag: <meta name="robots" content="nofollow" />, tell reptiles all links on this page without tracking.

(2) for a tag: <a href="login.aspx" rel="nofollow"> login </ a>, tells crawlers that page without tracking.

nofollow role

nofollow has three main roles:

1. Prevent untrusted content, the most common is spam on the blog and comments in order to obtain outside the chain of spam links, pointing to the page in order to prevent some of the trash pages and sites.

2 Paid links: To prevent paid links on Google's search results ranking, Google recommends using the nofollow attribute.

3 guide reptiles crawl valid pages: Avoid reptiles grab some meaningless pages, affecting reptiles crawling efficiency.

PR trim (Pagerank Sculpting)

nofollow abuse, in order to do some SEO largest search engine optimization, PR via nofollow to control the flow, can be well optimized certain pages. Of course, this optimization is more suitable PR has accumulated a considerable number of the old site. In order to prevent abuse of PR trim and nofollow, Google has weakened nofollow role, not only does not cause the previous nofollow PR flow while PR does not cause loss provisions nofollow now though it will not cause the flow of the target page PR, but original flows target page will be lost. For example, this page PR is 1, and there are 10 links on the page, one of which is nofollow links nofollow according to the previous provisions nofollow links to each non-target page will be 1/9 PR, containing links nofollow can not get PR, Google is now nofollow under the new provisions, non-nofollow links point to the target page can only get 1/10, nofollow links also can not get PR, which is a loss of 1/10 PR.

SEO recommendations

nofollow in Google's role has been very weak, so the site's PR SEO To control the flow, avoid links to spam pages, can only rely on manual audit approach.