Hello everyone! I fixed it for myself, please try, hopefully it will work for you. My environment: R410, R710 OMSA 8.1.0.1 iDRAC v1.99 Lifecycle controller 1.7.5.4 Firefox 39.0 Login to OMSA using IE or Chrome, go to Preferences -> General Settings, set SSL Encryption to Auto Negotiate and hit Apply. You’ll be notified to restart web server, click OK and look for “Options: Restart Web Server” link. Click on that, give it 30 seconds and enjoy on FF 39.0! In the same place you can change SHA-1 to better algorithm. Not sure if patch to OMSA helped, didn’t try with previous versions.
In Firefox version 39, some OMSA web site would give this error message: An error occurred during a connection to :1311. SSL received a weak ephemeral Diffie-Hellman key in Server Key Exchange handshake message. (Error code: ssl_error_weak_server_ephemeral_dh_key)  I suppose I need to reinstall new version of OMSA, or is it?  I haven't checked yet.  Does new version exist yet?  And is there some "fast and dirty" workaround because it would take me quite some time to update all my OMSA. Thanks
"weak ephemeral diffie-hellman key" error in FF39 prevents OMSA from being 
accessible