PageRank™ is passed from web-page to web-page. It does this through links, everytime you link to a page on your own website or to pages on a partner or an information website you pass across PageRank™. You vote for that page!
So this is a good thing for who you're linking to and can be a good thing for you also, it demonstrates a sense of sharing and helps Google™ and other search engines crawl the web, you have now become a source of links. However you are not yet trusted!
To be trusted you too have to grow your own PageRank and have others vote for you, but that's another post and tutorial all together. If, however, your interested in this check out the Understanding Search Engines DVD.
OK, so on with the topic in hand. What can you do when you wish to link, but not vote? In real world terms it's like telling someone you know a plumber but can't vouch for them as you haven't used them before. In this case you can direct Google™ not to follow a link. There are 3 ways to accomplish this;
- Meta tag directive
- Anchor (link) tag directive
- Robots.txt files
Meta tag directive
The meta tag directive is a small piece of code you add to your HTML head tag. It has a number of different settings, but in terms of PageRank voting, you need to use the 'nofollow' attribute setting as follows.
<!-- Other tags such as Title, meta description etc. -->
<meta name="ROBOTS" content="NOFOLLOW">
This instructs the search engine not to follow any links found on that web page. You can also instruct the search engine not to index the page by using the following snippet;
<meta name="ROBOTS" content="NOINDEX,NOFOLLOW">
Anchor (link) tag directive
Similarly to the meta tag directive, you are also able to add no follow instructions at the lower level of just a single link. You may have a number of links on a page and only a handful are not to be followed, in this instance using the Meta tag or robots.txt file is not suitable. You use this tag as follows;
<a href="http://www.targetsite.com/subpage.html" title="something interesting" rel="nofollow">Stuff I may not trust in the future</a>
The rel="nofollow" directs Google™ not follow this link.
A robots.txt file sits in the route folder of your website and provides search engines with hints of what it can and cannot crawl. Therefore the robots.txt file is more of a NOINDEX directive than a NOFOLLOW one. A basic file may look like this;
However, you can add specific instructions to certain crawlers by adding the crawler name to the User-agent like this;
This would have the effect of stopping Google™ from crawling the links folder but allowing other search engines to crawl it.
We hope this helps, please comment if you have any questions.