How can I create a certificate that Firefox will trust?

Question

Digital certificates

There is a site which is accessible by the user of a local network. Works on Apache on Win XP over HTTPS protocol. After updating Firefox to version 42, it began to require an SSL certificate. After trying to create a certificate using OpenSSL, The server certificate included a public key that was too weak (error code ssl_error_weak_server_cert_key) swears. How to create such a personal certificate for a site that will suit FF?
I created a certificate like this:
openssl genrsa -out privat.key 4096
openssl req -new -key privat.key -out server.crt -x509 -days 3650

Answer 1

probably easier to get free on startssl.com
habrahabr.ru/post/127643

Answer 2

Take your certificate and add it to the list of root (CA) in the FF settings