If you don't know what that means don't worry, if all goes to plan you won't even notice the change, but if I get it wrong the chances are that the site will disappear until it's fixed.
The other problem with DNS changes are that they take a few hours to take effect across the whole internet, so I won't necessarily know if there is anything wrong straight away. I'll have to make the change then keep an eye on everything throughout the evening until I'm happy everything has transferred across ok.
So, if you experience loss of service this evening please bear with me. Fingers crossed!
Chris