SEO试验第二期：nofollow标签和dofollow标签的作用

google关于nofollow的介绍

Together with Yahoo! and MSN, Google introduced the "nofollow" HTML microformat a few years ago, and the attribute has been widely adopted. Any link with the rel="nofollow" attribute will not be used to calculate PageRank or determine the relevancy of your pages for a user query. Any link with the rel="nofollow" attribute will not be used to calculate PageRank or determine the relevancy of your pages to a user query. (For example, if a spammer includes a link in your comments like this:

<a href="http://www.example.com/">This is a nice site!</a>
it will get converted to:
<a href="http://www.example.com/" rel="nofollow">This is a nice site! </a>
This new link will not be taken into account when calculating PageRank. This won't prevent spam, but it will avoid problems with passing PageRank.

By default, many blogging sites (such as Blogger) automatically add this attribute to any posted comments.

本次试验的目的就是为了判断nofollow标签到底有多大的作用