function Sniff() {

this.ns = false, this.ns4 = false, this.ns6 = false, this.ie = false, 
this.ie4 = false, this.ie5 = false, this.ie55 = false, this.ie6 = false;

var agent = navigator.userAgent.toLowerCase();
this.major = parseInt(agent.substring(agent.indexOf("msie")+5,agent.length));
this.minor = parseFloat(agent.substring(agent.indexOf("msie")+5,agent.length));
this.ns = ((agent.indexOf('spoofer')==-1) && (agent.indexOf('compatible') == -1));
this.ns4 = (this.ns && (this.major == 4));
this.ns6 = (this.ns && (this.major == 5));
this.ie = (agent.indexOf("msie") != -1);
this.ie4 = (this.ie && (this.major == 4));
this.ie5 = (this.ie && (this.major == 5) && (this.minor < 5.5));
this.ie55 = (this.ie && (this.major == 5) && (this.minor >= 5.5));
this.ie6 = (this.ie && (this.major == 6));

};

var sniff = new Sniff();