I just fixed that by setting: security.tls.version.max = 3 security.tls.version.min = 1 security.ssl3.rsa_fips_des_ede3_sha = false in about:config, aft

I just fixed that by setting: security.tls.version.max = 3 security.tls.version.min = 1 security.ssl3.rsa_fips_des_ede3_sha = false in about:config, after which it also said "Probably good" for FF26.