Thanks everybody, I checked the cookie page, all the boxes are checked for allowing cookies. I checked the cookie list, the name of the site, I'm having problems with, is listed there.
I've tried my user name and password, several times, also checked the (remember me) box. After using that box, my user id and password will show, when I go to the site,but, I still can't log-in. It keeps telling me to register.
Everything works fine using IE on that site. I guess I can switch back and forth between IE and FF, or register again using FF browser. I'm not even sure that will work, haven't tried it, yet.
There might be some advantages to having two different ids on the same web site. I never thought of that, funny.