safari access denied authentication failed behind proxy

Hi hello

I have proxy in my company, and my safari don't work, firefox is ok, he ask me my username and password for the proxy

And Safari don't work, he write me

" Access denied ( authentification_failed )

Your credentials could not be authenticated : "credentials are missing". You will not be permitted access until your credentials can be verified.

This is typically caused by an incorrect username and/or password but could also be caused by network problems. "

Wait your help

Thanks