function IsLayer(WhichID) {
	if (IsNS4) return (eval('document.layers.' + WhichID));
	if (IsIE4) return (eval('document.all.' + WhichID));
	if (IsNS6) return (eval('document.getElementById("' + WhichID +'")'));
	return false;
}

// show/hide layer
function ShowHide(WhichID, WhichState) {
	if (IsNS4 && IsLayer(WhichID)) eval('document.layers.' + WhichID + '.visibility = "' + WhichState + '"');
	else if (IsIE4 && IsLayer(WhichID)) eval('document.all.' + WhichID + '.style.visibility = "' + WhichState + '"');
	else if (IsNS6 && IsLayer(WhichID)) eval('document.getElementById("' + WhichID + '").style.visibility = "' + WhichState + '"');
}