ActiveWidgets 2.5 works on -
Other Mozilla-based browsers (Firefox 1.x, 2.x, Mozilla) will most likely work fine, but FF 3 is the only one tested.
ActiveWidgets 2.5 works on Windows (IE, Firefox, Safari, Opera, Chrome), Linux (Firefox, Opera) and Mac OS X (Safari, Firefox, Opera)
ActiveWidgets 2.0 supports all doctypes starting with 2.0.1 release (including both 'quirks' and 'standards-compliant' mode box models).