First, you will want to set up your Public Folder on your MobileMe account with a password. This allows you to share files in that folder without having to give out your main account password or keep your folder completely open. Once you have uploaded files to your iDisk's Public Folder log on to me.com and and login with your MobileMe credentials.
- Click the iDisk icon.
- Click the gear icon in the center of the window.
- Choose Preferences from the drop down menu.
- Select "Password-protect your public folder." and click "Change Password" to set a new Public Folder password.
- Click "Save" and you are all set to share your files.
Whenever I try to set a password for the public folder of my iDisk, it becomes totally inaccessible. I set the password through the Preferences panel and when I try to open the iDisk address in Safari, a panel drops down asking for user name and password. And that turns out to be an insurmountable hurdle: try the password you just defined in iDisk setting, it doesn't work; try your MobileMe user name and password, and it doesn't work.The issue that is not made immediately clear with your iDisk Public Folder password is that when users attempt to access it, they need to enter 'public' in the "Name:" field and then use the password you created and sent to them. There does not seem to be any rhyme or reason to this line of thinking, nor is it made expressly clear in Apple documentation.
For more on using your iDisk Public Folder to share files, read this Apple KB Article.