Adding or Accessing Yahoo Mail contacts on iPhone 4 or iPod Touch

UPDATE: 11/23/2010 -> I've been using this method for a while now and it works great!
*OCCASSIONALLY* after phone using up all of its battery, you may need to do this:
Settings->Safari->Clear Cookies. Then quit the Contacts application and restart it. If your phone supports multi-tasking make sure you completely quit the Contacts application. Then reopen contacts and go to your carddav.address.yahoo.com contacts -> they should reappear now

NOTE: if you've already added your Yahoo contacts (carddav.address.yahoo.com contacts), but then they disappear and are no longer visible, try:
-> hitting the home button twice to show all currently running background apps (on iphone 4)
-> hit the "-" on each of these in the lower screen (looks like your deleting them, but it's just terminating them from background process)
-> when all are terminated, reboot the iphone (hold the sleep, then slide to power off)
-> when started back up again, goto Contacts > All carddav.address.yahoo.com > and then these contacts should begin populating
-> I noticed that the "ContactsTool" and "ImportExportContact" apps that I downloaded from the App Store, can cause the Yahoo contacts to disappear and require this procedure


I found this info on Yahoo and it worked on my iPod Touch and iPhone 4. If you are running iPhone 4.0 software or newer, you will be able to sync your Yahoo! Contacts to your iPhone or iPod Touch without plugging it into your computer. You can check your current version by going to Settings, then General. From there choose About, followed by Version on your iPhone or iPod Touch device.
To sync your account:
Go to your iPhone or iPod Touch settings application
Tap Mail, Contacts, Calendars
Tap Add Account
Tap Other and then tap Add CardDAV Account
For the Server you need to enter carddav.address.yahoo.com
Now type in the Yahoo! ID and password you use to sign in to your Yahoo! Contacts
Once you click save, your device will verify your Yahoo! ID and password
(after this is done, if you go back to settings/contacts, under the advanced tab for carddav.address.yahoo.com, the settings Use SSL On, and Port 443 will show up)
Next time you open up your iPhone or iPod Touch Contacts app you will see a page allowing you to see your Yahoo! Contacts sync into your device Contact list.
If you'd like to have the contacts you add onto your iPhone automatically sync to Yahoo!, you will need to go back into the device Settings application. Click on Mail, Contacts, Calendar. Drag the page down to the Contacts section and change the default Contacts account that you would like to save Contacts to.
Note: Some characters in the password may not work (such as '#' and ' ') when setting up CardDAV. Depending on what version of the software you are using this may or may not be the case.
If you are having problems syncing your Contacts try going to settings->Safari->Clear Cookies. Then quit the Contacts application and restart it. If your phone supports multi-tasking make sure you completely quit the Contacts application.