iTunes Store and ports 80 & 443

I have a N600 C3700 modem-router.  All internet connections work fine, except to Apple's iTunes Store.  When I try to make a purchase, either the connection times out or the sign-in can't be verified.  I talked to Apple.  They checked their end, as well as my Apple ID and password.  All are fine, according to them.  So they told me to check ports 80 and 443 at my end.  Those ports need to be open, for me to make purchases on iTunes Store.  They did not specify outbound or inbound. 

So my question is:  On my modem-router are ports 80 and 443 open by default?  If not, how do I open them?

Thanks!