This problem can be caused by a variety of issues, including:

• Internet connectivity has been lost.
• The website is temporarily unavailable.
• The Domain Name Server (DNS) is not reachable.
• The Domain Name Server (DNS) does not have a listing for the website's domain.
• If this is an HTTPS (secure) address, click Tools, click Internet Options, click Advanced, and check to be sure the SSL and TLS protocols are enabled under the security section.