function isWin () { return (navigator.appVersion.indexOf ("Win") != -1); }
function isMac () { return (navigator.appVersion.indexOf ("Mac") != -1); }
function isIE () { return (navigator.appName.indexOf ("Explorer") != -1); }
function isNS () { return (navigator.appName.indexOf ("Netscape") != -1); }
function isWinIE () { return (isWin () && isIE ()); }
function isWinNS () { return (isWin () && isNS ()); }
function isMacIE () { return (isMac () && isIE ()); }
function isMacNS () { return (isMac () && isNS ()); }