The ability to change the DNS configuration of a web site is an important feature for many people. However, incorrect DNS modifications can take an entire web site down for an extended period of time. This is because DNS changes aren't instant (see the Tutorial below). If you make a mistake, it is possible that nobody will be able to connect to your site (including yourself). If you fix the mistake, it may take up to 72 hours for the repair to take effect.
There are several things you can do to prevent mistakes:
1. Read this document thoroughly.
2. Make sure you understand what A, CNAME, NS, and MX records do.
3. Contact your web host for additional help and guidance.
4. Don't make a major change without assistance.
With a little bit of practice, you will find that making DNS changes is very simple.