Javascript Code for Browser Dedection

var s;

var agt=navigator.userAgent.toLowerCase();
var is_major = parseInt(navigator.appVersion);
var is_minor = parseFloat(navigator.appVersion);

var is_nav = ((agt.indexOf('mozilla')!=-1) && (agt.indexOf('spoofer')==-1)
&& (agt.indexOf('compatible') == -1) && (agt.indexOf('opera')==-1)
&& (agt.indexOf('webtv')==-1) && (agt.indexOf('hotjava')==-1));
var is_nav4 = (is_nav && (is_major == 4));
var is_nav6 = (is_nav && (is_major == 5));
var is_nav6up = (is_nav && (is_major >= 5));
var is_ie = ((agt.indexOf("msie") != -1) && (agt.indexOf("opera") == -1));


function x()
{
alert(is_ie);
}