In the case that your domain is propagating from one server to another, your website may appear down. This is being your Internet Service Provider has not refreshed their DNS cache or your browser is still reading from your old dns server.
To resolve this type of issue you can flush your dns.
In Windows XP click on the Start Button
Then click on Run
Type in: cmd and hit enter
The black command prompt window will appear, type the following and hit enter : ipconfig/flushdns
You will then receive a confirmation that your DNS has been successfully flushed.
You can now close the command prompt and also close your web browser. Now re-open the borwser and try going to your website and the issue should be resolved!
Keep in mind the above solution will only work in Windows XP.
