adding www.outube.com to whitelist not working

I am using Parental Controls on my iMac and it effectively blocked access to YouTube (wwww.youtube.com). However, I woudl like to grant access to this site and added wwww.youtube.com to the list of allowed web sites ("whitelist"). Still not allowing access.... only if I turn off Parental Contrals (which I don't want to do) is access to YouTube possible... what am I possibly doing wrong?