function checkBrowser() {
    var output="";
    var agent = navigator.userAgent.toLowerCase();
    this.moz = (agent.indexOf('mozilla/5')!=-1);
    this.mac = (agent.indexOf("mac") != -1);
    this.ns  = (agent.indexOf('netscape')!=-1);
    this.op  = (agent.indexOf('opera')!=-1);
    this.ff  = (agent.indexOf('firefox')!=-1);
    this.ie5 = (agent.indexOf("msie 5") != -1);
    this.ie6 = (agent.indexOf("msie 6") != -1);
	this.ie7 = (agent.indexOf("msie 7") != -1);
	this.ie8 = (agent.indexOf("msie 8") != -1);

    output = "<link rel=\"stylesheet\" href=\"../css/zahnarzt_moz.css\" type=\"text/css\">";
    if (this.ns==true ) {
       output = "<link rel=\"stylesheet\" href=\"../css/zahnarzt_ns.css\" type=\"text/css\">";
    }
    if (this.op == true) {
	   output = "<link rel=\"stylesheet\" href=\"../css/zahnarzt_op.css\" type=\"text/css\">";
    }
    if (this.ff == true) {
	   output = "<link rel=\"stylesheet\" href=\"../css/zahnarzt_ff.css\" type=\"text/css\">";
	   docmenutop = 50;
    }
    if (this.ie5 == true) {
	   output = "<link rel=\"stylesheet\" href=\"../css/zahnarzt_ie5.css\" type=\"text/css\">";
    }
    if (this.ie6 == true) {
	   output = "<link rel=\"stylesheet\" href=\"../css/zahnarzt_ie6.css\" type=\"text/css\">";
    }
    if (this.ie7 == true) {
	   output = "<link rel=\"stylesheet\" href=\"../css/zahnarzt_ie7.css\" type=\"text/css\">";
    }
    if (this.ie8 == true) {
 	   output = "<link rel=\"stylesheet\" href=\"../css/zahnarzt_ie8.css\" type=\"text/css\">";
    }
    return output;
  }

  var browser_css = checkBrowser();
  document.write(browser_css);