I thought 25 sounded a little off, that version was a couple years back. FF only recently cut off support for old style NS plugins. Chrome never really supported them, and IE probably will never STOP supporting them (but Edge doesn't do plugins at all). I never understood WotC's decision to use Silverlight, which was basically already being phased out by MS when they started using it. I guess it was just based on having a crapton of existing C# code they thought they could reuse. I doubt it did them much good. Admittedly the 2010 era web application landscape was a lot harsher than it is now. You could actually build a very good CB these days online if you knew what you were doing. Not so much back then. (IE Angular, React, lots of server-side rendering, spin it up in AWS or Azure and run it under Cloud Foundry or something like that).