I'm not sure about your brand of modem, but with some at least yo need to reboot it after doing the port forwarding.
Also, quote: If you find that you can not pull up webpages, the problem is most likely the dns numbers you entered. Give your isp a call, and they will be able to tell you which dns servers to use. This is a question they answer all of the time. They will be able to tell you what you should use right away.