You may use any characters or HTML you want in the message, with the exception of <!-- comment tags -->. You will need to use the following special characters:
     [THIS INCLUDES INSIDE HTML TAGS!]
  To use a single quote ('),  use \' (backslash-quote)
  To use a backslash (\), use \\ (backslash-backslash)
To generate the same message for two seperate browsers, go like this:
  N3='Message for Netscape
3 and [mis]communicator'
  N4=N3
If they come out with Netscape or IE versions 5, you can just add new lines like so (unless they change the JavaScript specs, but they probably won't...)
  N5='whatever'
  IE5='whatever'
  WTV4='whatever' // this is assuming there isn't already a WebTV version 4...
Example:
<SCRIPT>
<!-- written by The Omega
//   http://members.xoom.com/the_omega/
//   the_omega@geocities.com
// You must leave these comments in to use the script
//  (hey, I wrote it. Let me have a little credit!)
var nme=navigator.appName.toLowerCase()
var ver=navigator.appVersion
N2='I see you\'re using Netscape 2'        // <--- indicated line
N3='I see you\'re using Netscape 3'        // <--- indicated line
N4='I see you\'re using [mis]communicator' // <--- indicated line
IE3='I see you\'re using IE 3'             // <--- indicated line
IE4='I see you\'re using IE 4'             // <--- indicated line
WTV3='I see you\'re using a WebTV browser' // <--- indicated line
X='No idea what browser...'                // <--- indicated line
name2="X"
if (nme.indexOf("microsoft")!=-1)
name2="IE"+ver.substring(0,1)
if (nme.indexOf("netscape")!=-1)
name2="N"+ver.substring(0,1)
if (nme.indexOf("webtv")!=-1)
name2="WTV"+ver.substring(0,1)
if(eval(name2)==null)
name2="X"
document.writeln(eval(name2))
//--></SCRIPT><NOSCRIPT>
<!-- The line below is also indicated -->
Hmmm... either you have a non-JavaScript capable browser or you have JavaScript disabled...
</NOSCRIPT>