There are a couple of reasons why Address AutoComplete may not work.

First, double-check to see if Address AutoComplete is enabled. To do this:

1. Click Options in the upper right of your Mail page.
2. In the “Management” category choose General Preferences.
3. Toward the bottom of the page, in the “Message Actions” section, you’ll see an AutoComplete setting. Make sure the "Use Address AutoComplete (default)" option is selected.

A few other things to check:

• Is the address that you’re typing in your Address Book? If not, it won’t AutoComplete for you.
• Do you have the latest Yahoo! toolbar? If not, AutoComplete may not work.
• Finally, you may have a compatibility issue with the browser you’re using. See the supported browser list below.

Supported Browsers:

• IE 6.0 and above for Windows
• Netscape 7.2 and above for Windows
• Firefox 1.x and above for Windows & Mac
• Safari 2.x and above for Mac

Remember, even if you can’t AutoComplete addresses, you can still insert contacts from your Address Book by clicking on the "Insert addresses" or "To:" links on your Compose page.