var net4 = (document.layers) ? true:false;
var net6 = ((navigator.appName.indexOf("Net") != -1) && !net4);
var ie5 = (document.getElementById && !net6) ? true:false;
var ie4 = (document.all && !document.getElementById) ? true:false;
var isMac = (navigator.appVersion.indexOf("Mac") != -1);
var dom = (document.getElementById) ? true:false;