The SSL error ssl_error_rx_record_too_long
in Firefox when accessing an Apache2 host can have different causes:
1) SSL is not enabled
Make sure that SSL is enabled in Apache2. The command a2enmod ssl
(Linux) will enable SSL.
2) Wrong vhost configuration
Check the configuration of the vhosts, read more about it here
3) Hostname not properly resolved
The file /etc/hosts
can sometimes cause problems because Apache might check there for resolving of names. Check this article
for more info.