How do I set up out of office autoreply when I'm on vacation. I have MobileMe accoutn

Go to icloud.com from your computer, sign into your account, click on Mail, click the gear-shaped icon on the top right and select Preferences, then go to the Vacation tab and check the box to automatically reply and compose your message in the text box below this.

Be sure to go back here and uncheck this setting when you return.