popUpWindow = function(URL,windowName,width,height) {
	var w = screen.availWidth;
	var h = screen.availHeight;
	var leftPos = Math.round((w-width)/2);
	var topPos = Math.round((h-height)/2);
	var defaults = "scrollbars=yes,resizable=yes,";
	var centerOnScreen = "top="+topPos+",left="+leftPos+",width="+width+",height="+height;
	// safari seems to need the trailer comma
	var options = defaults + centerOnScreen + ",";
	var msgWindow = window.open(URL,windowName,options);
	msgWindow.focus();
}