How to set cookie ONLY for my domain, except subdomains

[eluser]brianw1975[/eluser]
from http://content.websitegear.com/article/s...n_tips.htm

If you use cookies in your website, a cookie set from a subdomain
cannot be read from the main domain and vice versa because of the security
association feature tied to the domain which set it. This is also true for
session cookies, where, if the user is logged in on the main site, and
then moves to a subdomain, the subdomain site will not be able to access the
same session cookie, and will assign a new session (hence forcing the user
to login again). However, session persistence
across subdomains can be maintained by implementing URL rewriting instead
of session cookies.