From within the forum, they're wrong. From the SJG web site, they're correct. Something is appending a keyword (such as "GURPS") to the forum address, and that's often wrong. For example, clicking the GURPS link from within the forum goes to
http://forums.sjgames.com/gurps/, which doesn't exist. Clicking the GURPS link from the home page goes to
http://www.sjgames.com/gurps/, which does exist.