What are the minimum browser requirements for this to gracefully degrade?
The modal interface is IE11/newer only. I think for Firefuxxors it's 27.
I could probably make it work back to IE9 if I added a DIV and used display:table.
The tabbed interfaces one is likely the same, but honestly as I've stopped giving a flying **** about IE for most projects (since everyone else has -- bootstrap, react, angular) I'm not exactly going to bend over backwards on it.
Just as I really am no longer going to waste time trying to support FF 76/earlier.