Forums often receive a tremendous amount of traffic, and they often have great authority with the search engines. How many times have you searched for something online and discovered that a lot of the top links were to forums? Some forums use the tag “rel=nofollow” on their links, especially the link in signatures and posts.

This tag tells search engines not to follow those links, rendering them useless from a purely SEO standpoint. Of course, those links are still extremely...