Pay.gov currently only supports Internet Explorer 7 and 8, and Firefox 3.5. Should you already have IE 7 or 8 installed you can try the following configuration changes. Under Tools select Internet Options, then select Advanced tab: Under "Phishing Filter", select "Disable Phishing Filter", Uncheck "Warn about certificate address mismatch", Uncheck 'Warn if changing between secure and non secure mode'.