IE 4.x minimum

Though Scott Hanselman, in IE6 Warning - Stop Living In The Past - Get off of IE6, and others would like to see users upgrade to a newer version of Internet Explorer, it may take a long time to happen with some users.

This Government agency - to remain nameless - offers no incentive to upgrade according to this pop-up warning in which requires at least Internet Explorer version 4.0:

How they continue to keep their application compatible with a 12 year old browser I do not know, but they must be geniuses!