If you’ve never read Google’s Search Engine Optimization Guide, I strongly suggest you read it a few times and use the techniques it recommends to architect your site’s structure and appearance. Google is the most important audience acquisition tool you have and you need to follow their best practices if you have any hope of getting new readers in a scalable way.
In particular, you want to pay attention to the section of that document which describes the use of rel=”nofollow” attributes in hyperlinks. You should add these attributes to any destination link you don’t want the Google crawler to crawl.
Why would you do that?
Google penalizes your page rank if you link to sites that have poor quality content, including spam sites, link farms, and content farms. When you link to a site, any site, you are in effect recommending it. So, Google penalizes you if you recommend crummy content.
By default, many blog and forum systems tag outbound links in comments with nofollow tags. Self-hosted WordPress blogs are a good example of this.
But there are other times when you might want to manually use rel=”nofollow” attributes in hyperlinks.
A good example, is if you have a long list of links on a page, particularly if it’s off your home page. The Google crawler will stop indexing external links on a page when it gets to 100 or so. If you pass a lot of link love to other bloggers via home pages links like this, you may be far less effective than you realize.
There’s also a danger that the Google crawler will doc your sites reputation if it thinks that all you do is write posts that have lot and lots of external links in them. If you see content like this, it’s usually an indication that the author has nothing to say, and Google will penalize them for it. That’s how it treats link farms and aggregator sites, which it considers to be spam.
If you find yourself tempted to write content like this, and there are certainly benign examples where it’s useful, it’s a good precaution to add rel=”nofollow” tags to the links on the page. This defeats the link love that you might be passing along to others, but protects your reputation.
Google doesn’t mind long link lists which point back to internal content within a site, but lots of external links can backfire if you care about your Google page rank and reputation.