Getting the error as End User
If you’ve come across Firefox error code ssl_error_rx_record_too_long as a user, your options are limited because most problems resulting in this error are web server related.
The best course of action is to clear your browser’s cache and try again. Possibly try to use another browser and see if that solves it. The likely reason for it is that you may have visited that same site in the past before it had SSL enabled, and the old version is now cached in your browser.
If that still does not solve the problem, ensure you’re upgrading and running the latest version of Firefox and alternatively, ask the site administrator to look into it.
Getting the error as Administrator
If you encounter the Firefox error code ssl_error_rx_record_too_long while enabling SSL or otherwise configure your web sites, the following issues may be present in your system:
Port 443 or HTTPS is not enabled – instead of <VirtualHost *> or <VirtualHost *:80>, use <VirtualHost *:443> . Specifying the correct port along with properly configured certificates is vital.
Too many redirects between ports 80 and 443 – if you just enabled SSL, you may want to redirect user that are still requesting http to https. The users browser cache and some frameworks like WordPress may still no play along. Users may have to clear their cache and site admins have to ensure that their sites in WordPress have been changed to https in Settings -> General.