//navigators detection
isNS4 = (document.layers) ? true : false;
isIE4 = (document.all && !document.getElementById) ? true : false;
isIE5 = (document.all && document.getElementById) ? true : false;
isNS6 = (!document.all && document.getElementById) ? true : false;

//css for each browser
function styles()
{
  if (isNS6)
   {return '<link rel="stylesheet" type="text/css" href="styles/NS6styles.css" />';}
  else if(isIE4)
   {return '<link rel="stylesheet" type="text/css" href="styles/IE4styles.css" />';}
  else if(isIE5)
   {return '<link rel="stylesheet" type="text/css" href="styles/IE5styles.css" />';}
  else if(isNS4)
   {return '<link rel="stylesheet" type="text/css" href="styles/NS4styles.css" />';}
}
document.write(styles());