// 
if(parseInt(navigator.appVersion)>=4)
{
   if(navigator.appName=="Netscape")
   {
      if(parseInt(navigator.appVersion)<5)
  	      {		  
	document.write("<link rel='stylesheet' href='aa.css'>");
		  
	//alert('Netscape Navigator 4+');
      }
      else
      {
	document.write("<link rel='stylesheet' href='aa.css'>");
	//alert('Netscape 6');
      }
   }
   else if(navigator.appName=="Microsoft Internet Explorer")
   {
      document.write("<link rel='stylesheet' href='aa.css'>");
//	   alert('Internet Explorer 4+');
   }
}