ActiveWidgets 2.5 works on -
Other Mozilla-based browsers (Firefox 1.x, Mozilla) will most likely work fine, but FF 2.0 is the only one tested.
ActiveWidgets 2.5 works on Windows (IE, Firefox, Safari, Opera), 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).