function Is(){
var agent = navigator.userAgent.toLowerCase();
this.major = parseInt(navigator.appVersion);
this.minor = parseFloat(navigator.appVersion);
this.ns  = ((agent.indexOf('mozilla')!=-1) && ((agent.indexOf('spoofer')==-1) && (agent.indexOf('compatible') == -1)));
this.ns4 = (this.ns && (this.major >= 4));
this.ie   = (agent.indexOf("msie") != -1);
this.ie4  = (this.ie && (this.major >= 4));
this.opera   = (agent.indexOf("opera") != -1);
this.win   = (agent.indexOf("win")!=-1);
this.mac   = (agent.indexOf("mac")!=-1);
}