DNS (Domain Name Servers) tell computers how to find each other over Internet. When you type an address in your browser, your ISP (Internet Service Provider) checks with it's domain name server (DNS) to determine where to send you.
http://www.domain.com ---> Check with DNS ---> DNS says domain.com = 192.168.0.1 ---> You are taken to web site.
Why does this happen?
It happens because your domain name won't always have the same IP address. Each server on the Internet has an IP address (a numerical address like a phone number). Every time you change web hosts, you are changing servers (and therefore changing IP addresses).
Domain name servers keep a record of your domain name and what IP address (server) it should point to.
Why must I put my web host's name servers (DNS) in my domain record?
As you learned above, name servers tell the Internet how to find you. When you edit the name servers in your domain record, you are telling the Internet which name server provides the most up-to-date directions. If you don't change the name servers in your domain record (let's say you use your old web host's DNS), then your web site will point to a server that isn't hosting your domain. Or, if the old web host deleted you from their DNS, your domain wouldn't work at all.
Why does it take so long for my site to start working?
When you change web hosts (addresses) or register a domain for the first time, the new DNS information has to reach every other name server (DNS) on the Internet. Your site may work in as few as 4 hours, but the average waiting time is 24-72 hours. This delay occurs because most name servers (DNS) choose to periodically check for updates. That is, they aren't "live." Periodic checking is done because constant checking often slows down the server.
Why is my domain pointing to my old host, even though I cancelled my account with them?
There could be several reasons for this:
1. Their name servers are still in your domain record.
Solution: Update your domain record with your new web host's name servers (DNS).
2. They haven't removed your domain record from their name servers.
Solution: Ask them to remove your domain record, or follow the solution in #1 if you have a new web host.
3. DNS propagation hasn't taken place yet. This will happen even with your new web host's DNS in your domain record.
Solution: Wait 24-72 hours and contact your new web host if the problem persists.
Why can some people reach my new site but I can't?
Their ISP has more up-to-date DNS records than your ISP. Be patient, as your new site will appear within 24-72 hours.
Is there some way to view/access my site even though the DNS hasn't changed yet?
Yes. You may access your site at http://ip.address/~username and you may access the control panel at http://ip.address/config. If you don't know the IP address of the server, please ask your web host for it.