function browserName() {
  // IE
  if (navigator.appName == "Microsoft Internet Explorer"){
    return 0;}
  if (navigator.appName == "Opera"){
    return 1;}
  else{
    return 2;}
}

var intName = browserName();

if (intName == 0) {
  // IE
  document.write("<link rel='stylesheet' type='text/css' href='css/ie-style.css'/>");

} else if (intName == 1) {
  // opera
  document.write("<link rel='stylesheet' type='text/css' href='css/opera.css'/>");

} else {
  document.write("<link rel='stylesheet' type='text/css' href='css/moz.css'/>");

}