Seems to be this link: http://www.harleyhowto.com/forum/register.php

You posted with a very old Firefox/3.0.5 version from 2008.
Any reason why you still use such an old version (3.0.19 was the last 3.0.x) and have updated to Firefox 3.5 or 3.6 ?

I'm not sure why you believe that I'm running an outdated version of firefox but according to my files I'm running product version 3.6.12. In the support notification I received questioning the file version running on my computer, the link I had a problem with http://www.harleyhowto.com/forum/register.php\ was also included. When I clicked on the link I went directly to the site with no problem. Then I opened the original email containing the same link, clicked and went to 404 NOT FOUND ! I'm going back to the web site and go through the registration process again and keep my fingers crossed hopping it works when they send a new verification email . I will post the outcome, either pos. or neg and may be asking for further help. Thanks, debreeze

Take look at your UserAgent as websites see your browser in the More system details... next to your original posting.
http://en.wikipedia.org/wiki/User_Agent

See this for fixing it:
https://support.mozilla.com/en-US/kb/Websites+or+add-ons+incorrectly+report+incompatible+browser

Something went wrong with the link the first time (a \ got appended) and I edited my post and removed the backslash to correct that.

So this is the correct link: http://www.harleyhowto.com/forum/register.php
You may have some GET data appended to the link (?xxx=xxx), so you may need to copy and paste the full link in the location bar.

If you do not have the forum part in the link in the original mail then try to add it because the error message suggests that you used a link like http://www.harleyhowto.com/register.php