This might mean that someone’s trying to fool you or steal any info you send to the server. You should close this site immediately.
Go to your Start page
Details
The website’s security certificate is not yet valid or has expired.
Error Code: DLG_FLAGS_SEC_CERT_DATE_INVALID
Go on to the webpage (Not recommended)
It could be a cache problem. I just can't believe a reputed site like Rockettheme will allow its license to expire.
UPDATE: Just now I tried Chrome. and I didn't see the warning. If Chrome finds the site secure, I suppose it is something that is to be fixed at our end.