Do not allow AutoComplete to save passwords
User Configuration\Administrative Templates\Windows Components\Internet Explorer
Disables automatic completion of user names and passwords in forms on Web pages, and prevents users from being prompted to save passwords.
If you enable this policy, the User Names and Passwords on Forms and Prompt Me to Save Passwords check boxes appear dimmed. To display these check boxes, users open the Internet Options dialog box, click the Content tab, and then click the AutoComplete button.
If you disable this policy or don't configure it, users can determine whether Internet Explorer automatically completes user names and passwords on forms and prompts them to save passwords.
The Disable the Content page policy (located in User Configuration\Administrative Templates\Windows Components\Internet Explorer\Internet Control Panel), which removes the Content tab from Internet Explorer in Control Panel, takes precedence over this policy. If it is enabled, this policy is ignored.