The description of the rules for password complexity has been corrected. The new description is more precise about what attributes are checked and more accurate of the categories of characters that must be included in the password in order to meet complexity requirements.
The updated content is at http://technet.microsoft.com/en-us/library/cc786468(WS.10).aspx.
Unfortunately the original incorrect version is found in several other places on www.microsoft.com. We are trying to get these incorrect references updated or removed, but in the meantime be aware that these references are not accurate:
Justin Hall [MSFT]
Active Directory Documentation Team