First check that you are entering the correct username and password. If they are okay then one of two things may have happened: if COPPA support is enabled and you clicked the I am under 13 years old link while registering then you will have to follow the instructions you received. If this is not the case then maybe your account need activating. Some boards will require all new registrations be activated, either by yourself or by the administrator before you can log on. When you registered it would have told you whether activation was required. If you were sent an email then follow the instructions; if you did not receive the email then check that your email address is valid. One reason activation is used is to reduce the possibility of rogue users abusing the board anonymously. If you are sure the email address you used is valid then try contacting the board administrator.