Why does Internet Explorer say "There is a problem with this website's security certificate"?

If you use Microsoft Internet Explorer version 6 or earlier, or if you use Internet Explorer under Windows XP (or Windows 7 with certain configuration settings), you may see the message "There is a problem with this website's security certificate" when viewing secured (SSL) pages on ProZ.com servers.

This happens because those versions of Internet Explorer don't understand the technology ProZ.com uses to serve secure SSL web pages. (ProZ.com switched to this new technology, called SNI, in November 2014, to increase security for ProZ.com-hosted web applications). 

You can resolve this issue by taking one of the following actions:

• If you use Internet Explorer version 6 or earlier, upgrade to a more recent version.
• If you use Windows 7 and see this warning in Internet Explorer, you may need to enable the TLS protocol. Go to Control Panel->Internet Options->Advanced, and under "Security", tick the checkbox for each of the options labeled "Use TLS {version}".
• If you use Windows XP or earlier, no version of Internet Explorer supports this secure site technology. You can use a different browser such as Chrome or Firefox to view the secure pages without warnings.

See this blog post at the Microsoft Developer Network for more details.