Basically Rh supports those three browsers only plus Safari on a Mac.
Because of the way Firefox changed their version numbering, I think it became impossible to keep up with it.
There is also the issue that say Rh10 will have issues in say IE11 without a patch and work with the patch.
I will try to get some more detailed information but don't hold your breath.
See www.grainge.org for RoboHelp and Authoring tips
Could I ask you to clarify and perhaps expand on your third sentence in your 4/7 response - specifically with regard to a patch.
One of our clients reports the it is using the IE 11 browser with our RH10 RoboHelp HTML output. The client is unable to view/access the TOC, Glossary, Searh and Index functions.
Is there a patch available that would resolved this issue at the production end or at the client's end?