// Browsercheck
function browserCheck() {
	var agt = navigator.userAgent.toLowerCase();
	this.ie4 = (document.all) ? true : false;
	this.ns4 = (document.layers) ? true : false;
	this.dom2 = (document.getElementById) ? true : false;
	this.ie5 = (this.ie4 && this.dom2) ? true : false;
	this.ns6 = (!this.ie4 && this.dom2) ? true : false;
	this.mac = (agt.indexOf('mac') != -1) ? true : false;
}
var is = new browserCheck();

if (is.ns4)

      {

        // Der Netscape-Browser wird verwendet
        var x = window.open ('ns4.html','ns4');
		window.close();
		x.focus();
      }