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) &&
  (agent.indexOf('opera') == -1) &&
  (agent.indexOf('webtv') == -1));
  this.ns2 = (this.ns && (this.major == 2));
  this.ns3 = (this.ns && (this.major == 3));
  this.ns4 = (this.ns && (this.major == 4));
  this.ns6 = (this.ns && (this.major >= 5));
  this.ie = (agent.indexOf("msie") != -1);
  this.ie3 = (this.ie && (this.major < 4));
  this.ie4 = (this.ie && (this.major >= 4) &&
  (agent.indexOf("msie 5.0") == -1));
  this.ie5 = (this.ie && (this.major == 4) &&
  (agent.indexOf("msie 5.0") != -1));
  this.ieX = (this.ie && !this.ie3 && !this.ie4);
 }

 var is = new Is();

 if(is.ie || is.ns6)
  document.write("<link rel='stylesheet' type='text/css' href='../style/iestyle_index.css'>");
 else if(is.ns)
  document.write("<link rel='stylesheet' type='text/css' href='../style/nnstyle_index.css'>");