I have already send an email to support@lunarpages and opened a ticket. but still now, near 1 day, I didn't get any response. So I think I'd better to post here to get some help.

I bought a domain:  xxxx.com, and change nameserver to be ns1.lunarservers.com   ns2.lunarservers.com (My host is also in lunarpages)

And I add a "add-on" domain.  But I couldn't visit xxxx.com.

So what is wrong?

Thanks very much, MrPhil.

I couldn't open xxxx.com. Maybe it needs time?

Well, it always needs some time for news of your changes (pointing the domain to a new nameserver) to spread across the Internet's Domain Name System. When it gets to your local ISP, you should be able to then "resolve" xxxx.com. Usually this happens in less than 24 hours, but sometimes it takes up to 72 hours. If 72 hours have passed and you still cannot see xxxx.com, the first thing to do is to check with the registrar -- do you have some sort of control panel with your registrar, to see the settings for xxxx.com? Check to make sure the changes you made were accepted and are on their way to the world. Next, bring up a whois server such as http://whois.domaintools.com and enter xxxx.com. It will tell you what it knows about the domain.

If xxxx.com is pointing to your LP account, to the proper nameserver (the same ones as your existing primary account), what kind of error do you get? Does your browser report that it is unable to resolve xxxx.com, or do you get "something" but not the page you expected? "Can't open" is too vague.