version=0;


browserName = navigator.appName; 
browserVersion = parseInt(navigator.appVersion); 

if (browserName == "Netscape") 
{
  if ((browserVersion < 3) && (navigator.userAgent.indexOf("OS/2") == 0)) version = 0;
  else
  { 
    if (browserVersion < 4) version = 1; 
    else version = 2;
  }
} 
else 
if (browserName == "Microsoft Internet Explorer" && browserVersion > 3) 
{
  version = 3;
}


if (version == 2) 
{
  document.write('<link rel="stylesheet" href="system/nn_main.css">');
} 
else if (version==3) 
{
  document.write('<link rel="stylesheet" href="system/ie_main.css">'); 
}