Why IE7 fails Windows login while Firefox succeeds?
Question: I have a WCF service hosted in IIS6 that uses Integrated Windows Authentication. When connecting from Firefox, I am prompted for Username/Password and when I enter them, the service works as expected. With IE7, I am also prompted (no automatic login happens) and enter the Username/Password but then I am prompted again and then the login fails. In the server logs there is a message "Authentication failed for HTTP(S) connection" Answer : The resolution is to open the Advanced tab of the Internet Options dialog (under the Tools menu of IE7) and turn off the option "Enabled Integrated Windows Authentication". Be sure to restart IE7 for this setting to take effect. Turning off this option tells IE7 to use the NTLM authentication rather than try (and fail) Kerberos authentication. See here for more information on this topic.