Sometimes there is an issue with your DNS resolvers caching the domain name to IP mapping. When you're trying to go to the domain, it's actually pulling up an old IP address instead of looking for a new one and finding the correct record. So, to expedite this very common problem of cached DNS, please do the following steps.

Microsoft Windows Vista and Windows 7

Close your application (e.g. browser or email).

Click the Start orb and follow All Programs > Accessories, look for Command Prompt. Be sure to right click on Command Prompt and choose "Run as Administrator". When the black screen appears, type the following command and hit enter.

ipconfig /flushdns

Restart your application (e.g. browser or email).

Microsoft Windows XP

Close your application (e.g. browser or email).

Go to the Start menu, choose Run, type cmd and hit OK. When the black screen appears, type the following command and hit enter.

ipconfig /flushdns

Restart your application (e.g. browser or email).

Mac OSX

Navigate to your Applications folder, open Utilities, and double click on Terminal. Type the following command and hit enter.

dscacheutil -flushcache

That command should work on Mac OS X 10.5 (Leopard), 10.6 (Snow Leopard) and 10.7 (Lion). If the above command is not available, you can try the other flush DNS command as follows which should work on Mac OS X 10.4 (Tiger):

lookupd -flushcache

Don't worry if either command says something like "Not found".

Restart your application (e.g. browser or email).

Linux

Note: Different distributions and versions of Linux may have slightly different commands due to differences in configuration. One of the commands below will probably work.

Open up a root terminal window (Ctrl+T in Gnome). Type the following command and hit enter.

/etc/init.d/nscd restart

You may need to use sudo depending on your installation instead:

sudo /etc/init.d/nscd restart

Some distributions support this command:

sudo /etc/init.d/dns-clean start

Or support this command:

sudo service nscd restart

Some installations may have NSDS located in another directory, like the following example. You may need to locate where it is installed to be able to execute the correct command.

/etc/rc.d/init.d/nscd restart

Restart your application (e.g. browser or email).