//  Check for Netscape 4 or above or IE4 or above and WEBTV, MAC

NS = (document.layers) ? 1:0
IE = (document.all) ? 1:0
NOWEBTV = (navigator.userAgent.indexOf("WebTV") == -1)
DHTML = ((NS || IE) && NOWEBTV);
MAC = (navigator.userAgent.indexOf("Mac") != -1);