Google and other search engines don't like sites that try to artificially increase the PageRank of sites by adding lots of links. These are called link farms, and linking to one can lower your own PageRank score. But how can you tell if it is a link farm?
The best way to tell if a site is considered a link farm by Google is to find out it's PageRank. And the best way to do that is to install the Google toolbar in your browser (for IE and Firefox). Then surf to the page in question. Since PageRank is a Google technology, it's best to ask the source what they think.
The lower the PageRank, the more likely it is that Google thinks the site is some type of bad neighborhood. And Google doesn't like it when you link to bad neighborhoods, as linking implies that you think that site is high quality. So you should avoid linking to bad neighborhoods.
Another tool you can use to check pagerank is iWebTool's PageRank checker. This tool and others like it (search for "PageRank checker" in a search engine to find more) use various methods to determine what Google will give as the PageRank for a given page. I like this tool because it queries many of the different Google datacenters to find out what all of them give as PageRank for the site. But it sometimes gives strange answers (like 57 or 16 when the highest rank Google gives is 10). So don't use this site as your final answer. Google itself is still better
High PageRank is Better Than Low
The higher the PageRank, the less likely it is to be a link farm. And if the site has a PageRank that is higher than your site's PageRank (and it's a related topic), you might want to ask them to link to you as well.
My rule of thumb is that if the site has a PageRank of 0 I don't link to it. If it's got a PageRank that's lower than my PageRank I evaluate the site and decide if I think it's high enough quality to link to. Just because a site has a low PageRank doesn't mean it's bad, it could just be new.
If Google is ranking a page as 0, there could be several reasons:
- It is a link farm or other bad neighborhood
- It's too new to have been ranked
- The datacenter you're checking is down
Other Ways to Check for Link Farms
Sometimes, you can't get a definitive answer from the Google toolbar, or you don't want to install it. Then how can you tell if a site is a link farm? There are two things you can do:
- Rely on your intuition - If you think a site is a link farm, it probably is. And even if it isn't, your readers might think so, and it's important to them that links they click on lead to high quality sites.
- Evaluate the site for SEO no-nos - If they are committing any of the "Avoid" or "Avoid or Get Banned" techniques listed in my SEO Tips and Tricks article, then they may be a link farm or bad neighborhood. And linking to them would only hurt your site.
Keep in mind that the Google PageRank can be delayed. So a spammer might buy a domain that has a really high PageRank and turn it into a link farm before Google has a chance to adjust the ranking down. So if you think a site is a link farm, even if it has a PageRank of 10, I wouldn't link to it.