How to detect a browser type in JavascriptV?

I found this very useful script in the internet and I just want to share it's usability. This script can be applied if ever you want your system to detect and inform the user that he or she is using an Internet Explorer Browser.

The Code:
<!--THIS WILL DETECT INTERNET EXPLORER BROWSERS-->
<script language="JavaScript"
type="text/JavaScript">

 if(navigator.appName == "Microsoft Internet Explorer")
{
 alert("This site works best with Mozilla Firefox.\nThank You!")
close();
}
</script>

Thanks to the Original Author.