if (navigator.userAgent.indexOf("Mac") != -1)
{
 {
  if ( ( navigator.userAgent.indexOf('MSIE') != -1 ) || ( document.getElementById ) ) 
  {
   document.write('<link rel="stylesheet" type="text/css" href="styles/mac_ie.css">');
  }
  else
  {
   document.write('<link rel="stylesheet" type="text/css" href="styles/mac_ns.css">');
  }
 }
}
else if (navigator.userAgent.indexOf('Linux') != -1)
{
 {
  if (navigator.userAgent.indexOf('Netscape')) 
  {
   document.write('<link rel="stylesheet" type="text/css" href="styles/linux_ns.css">');
  }
  else
  {
   document.write('<link rel="stylesheet" type="text/css" href="styles/linux_ie.css">');
  }
 }
} 
else
{
 if ( ( navigator.userAgent.indexOf('MSIE') != -1 ) || ( document.getElementById ) ) 
 {
  document.write('<link rel="stylesheet" type="text/css" href="styles/win_ie.css">');
 }
 else
 {
  document.write('<link rel="stylesheet" type="text/css" href="styles/win_ns.css">');
 }
}