Your Internet browser, computer, and ISP all cache (store) the information that tells them where a domain name lives (server). A domain name has nameservers that tell on which IP address the data resides. When you switch servers, the domain name stays the same but the nameservers and the IP address behind the name will change. It sometimes takes some time for this change to propagate across the Internet. Here are some tips to see your site on the new server.