How to make firefox independent frm msn?

I applied parental controls to MSN for my son, and i downloaded firefox to use on my own. he doesnt know that it’s another browser. Somehow, firefox uses msn parental controls and it wont go to sites that msn blocks, and if i dont sign into msn it wont even go anywhere. and if the site is allowed by msn, some image sources arent. how can i make firefox and msn separate on a NON admin account?