It's sad that lists.gnu.org is running obsolete TLS 1.0 crypto with weak 1024-bit DH. Either upgrade to TLS 1.2 with reasonable cipher suites, or just go back to plain HTTP.
You can find that information on the security tab of your browser's developer tools. You can also find a lot more info about any site's HTTPS configuration at ssllabs.com. Here's the report for lists.gnu.org: https://www.ssllabs.com/ssltest/analyze.html?d=lists.gnu.org
A good first step is disabling SSL 3.x and TLS 1.0 in your daily browser. I would also recommend the excellent Qualys SSL Server Test: https://www.ssllabs.com/ssltest/
