"...Firefox instead saves that site an 'exception'" what does this mean, can you please elaborate :-?

Under options... security... the 'Passwords' area, with the 'Remember passwords for sites' box checked, there is an 'Exceptions' button, leading to a list of the sites that are 'exceptions' to 'remember passwords for sites'. When I answer the password remember popup by hitting 'yes', rather than saving that password, Firefox instead saves that site in the 'Exceptions' list, for which passwords are never saved.