browserName = navigator.appName;
browserVer = parseInt(navigator.appVersion);

var ns = (browserName == "Netscape" && browserVer <6);
var ie4 = (browserName == "Microsoft Internet Explorer") && navigator.appVersion.indexOf('MSIE 4')>0;
var ie5 = (browserName == "Microsoft Internet Explorer") && navigator.appVersion.indexOf('MSIE 5')>0;
var ie = (browserName == "Microsoft Internet Explorer");

var mac = (navigator.userAgent.indexOf("Mac") != -1);