This article was previously published under Q296688
If a user is prompted for his or her credentials from a Web server that supports Windows NT Challenge/Response authentication, a dialog box with three input lines (for the user ID, password, and domain) is presented to the user. If the user ID, password, or domain entry contains a special character with a code point outside of the range from 32 to 126, the user's account is not granted access to the resource. If the password contains the special character, domain policies may force the account to be locked out after multiple retries.
The input fields in Internet Explorer are interpreted as ASCII input fields. Input that is entered by using the keyboard is encoded with the ANSI code page. The domain controller detects that an incorrect user ID or password has been typed because the character mapping between ASCII and ANSI is different for multiple characters (including language-specific special characters such as the German umlaut character).
Only characters that are identical in ASCII and ANSI are treated correctly. These characters have the same mapping in ANSI and ASCII: