How to accept insecure connection in Firefox 39+?

When I try to open a webpage, I get an ssl_error_weak_server_ephemeral_dh_key error in Firefox.

According to my googling the keys are weak, there is a security hole, I'm not safe, etc. Great, Firefox protects me. My only problem is that this is an intranet connection, so I'm pretty sure that nobody will try to hack me, IT just didn't update that server in a long time.

If I remember right in previous versions (I don't exactly know which versions, but then the error message included a yellow sign with a police officer too. Now I'm on 39.0) Firefox had an option to accept such connections. Is there a hidden way to still accept insecure connections like this? Maybe something in about:config that I can temporarily change manually?

I got an answer from another source, but I'll also post it here for future reference:

Apparently Firefox's about:config does have settings for disabling security protocols. In my case disabling security.ssl3.dhe_rsa_aes_128_sha and security.ssl3.dhe_rsa_aes_256_sha forces Firefox to use a stronger cypher and I can access the same page from Firefox too, without waiting for IT to fix it.

I don't know why, but it works.

The best answer is to ask IT to fix it, but as you said in your comments, you're more desperate for a quicker fix.

Also as per the comments, try a different browser.

Since Chrome works for you, use that!