Why should you use the rel="nofollow" tag ?
The rel=nofollow isn’t a real meta tag but more of a html description. It is often used on blogs, forums and guestbooks. But it is also possible to use it in your website if you don’t want certain links (intern or extern) to be followed and as a result leak pagerank. By adding the rel=nofollow you let the spidersknow that you didn’t add the link yourself but it was placed due to a blog or forum and therefore not necessarily approved. This doesn’t mean that spiders will reject the link. It just indicates that the link has no connection with your own website. Your website won’t be harmed in case there is a link to your website with a rel=nofollow.