A discrepancy would be a signal that hackers are rerouting Web traffic. Currently, browsers alert users when a site has a bad certificate, but many users don't know what to do about that. Some click through to malicious sites, while others skip over harmless sites that use "self-signed" certificates.
The Carnegie Mellon program is a free download for use with the latest version of Firefox.
On the 'Net: http://www.mozilla.com/en-US/firefox/
