Javascript判断browser类型及版本

<script language="javascript">
if(navigator.appName == "Microsoft Internet Explorer")
{
  if(navigator.appVersion.match(/7./i)=='7.')
  {
    //document.write("<LINK href='/css/index_ie7.css' type=text/css rel=stylesheet>");
    confirm("Current web browser is IE 7.");
  }
  else
  {
   confirm("Current web browser is IE 6.");
  }
}
else if(navigator.appName == "Netscape")
{
   confirm("Current web browser is Mozilla FireFox.");
}
else
{
   confirm("Unknown browser.");
}
</script>