If you get the above problem while you're browsing in XP or 2003:
1. Check your date and time settings if they're correct.
2. Your OS has not been updated for using the newest encryption, announced for Certificate Authorities in Windows Server 2008. (Hotfix for XP and 2003 is available here:
3. The owners of the websites haven't updated the SSL certificates used on their websites, usually meaning that the site isn't managed by them anymore.
4. Your internet connection is insecure, tapped and your computer is receiving phished or modified data. Avoid using the link at all costs especially if this link belongs to a bank, social site, mail or such other services, because your identity and credentials(such as passwords) may be compromised by the perpetrators responsible for this.
