If you want to do this, you'll need to modify the behaviour of the ShowMessage() function:
function ShowMessage(Feedback){
var Output = Feedback + '<br /><br />';
document.getElementById('FeedbackContent').innerHTML = Output;
var FDiv = document.getElementById('FeedbackDiv');
topZ++;
FDiv.style.zIndex = topZ;
FDiv.style.top = TopSettingWithScrollOffset(30) + 'px';
FDiv.style.display = 'block';
ShowElements(false, 'input');
ShowElements(false, 'select');
ShowElements(false, 'object');
ShowElements(true, 'object', 'FeedbackContent');
//Focus the OK button
setTimeout("document.getElementById('FeedbackOKButton').focus()", 50);
//
}
What you'll need to do is add another setTimeout call like this:
setTimeout("document.getElementById('FeedbackDiv').style.display = 'none')", 5000);
which should hide the feedback div after 5000 milliseconds.
I haven't tested this, by the way.
Hope this helps,
Martin