var _agent = navigator.userAgent.toLowerCase();

var _win = (_agent.indexOf('win') != -1);
var _mac = (_agent.indexOf('mac') != -1);

var _major = parseInt(navigator.appVersion);
var _minor = parseFloat(navigator.appVersion);

var _ns    = ((_agent.indexOf('mozilla') != -1) && (_agent.indexOf('compatible') == -1));
var _ns2   = (_ns && (_major == 2));
var _ns3   = (_ns && (_major == 3));
var _ns4   = (_ns && (_major == 4));
var _ns4up = (_ns && (_major >= 4));
var _nav   = (_ns && ((_agent.indexOf(';nav') != -1) || (_agent.indexOf('; nav') != -1)));
var _ns6   = (_ns && (_major == 5));
var _ns61  = (_ns6 && (_agent.indexOf('netscape6/6.1') != -1));
var _ns62  = (_ns6 && (_agent.indexOf('netscape6/6.2') != -1));

var _ie    = (_agent.indexOf('msie') != -1);
var _ie3   = (_ie && (_major < 4));
var _ie4   = (_ie && (_major == 4) && (_agent.indexOf('msie 5') == -1));
var _ie4up = (_ie && (_major >= 4));
var _ie45  = (_ie && (_minor == 4.5));
var _ie5   = (_ie && (_major == 4) && (_agent.indexOf('msie 5') != -1));
var _ie5up = (_ie && !_ie3 && !_ie4);
var _ie6   = (_ie && (_major == 4) && (_agent.indexOf('msie 6') != -1));