Symptoms: IE displays error page when browsing to page. Disabling authentication fixes this.
Note: This Knowledge Base article references software which is not maintained or supported by Cisco. The information is provided as a courtesy for your convenience. For further assistance, please contact the software vendor.
IE6 and IE7 does not allow setting cookies for two-letter domain names as this could be a security risk, because some Top Level Domains (TLDs) require an additional two-letter subdomain for any domain by default and setting -2-letter cookies would mean that the cookie would be shared across any of those sites, posing a security risk.
One example would be the domain: example.co.uk.
If one was to set a cookie for co.uk, it's contents would be sent to any of UK's commercial websites.
This is an IE issue and there is nothing the WSA can do about it, because the cookie is necessary for transparent authentication, especially with cookie surrogates. There is a registry key setting for IE6 to change this behavior. The article below documents information about the registry setting: http://support.microsoft.com/kb/310676