it comes with DW:
CODE-->Snippets--->Javascripts--->Browser Functions-->....
=================================================
<script>
------------------
function browserVer4Detect()
{
if(navigator.appVersion.substring(0,1) < 4)
URLStr = "1.html";
else
URLStr = "2.html";
window.location = URLStr;
}
-------------------
function platformDetect()
{
if(navigator.appVersion.indexOf("Win"

!= -1)
{
alert("Windows"

;
}
else if(navigator.appVersion.indexOf("Mac"

!= -1)
{
alert("Macintosh"

;
}
else alert("Other"

;
}
---------------------
// Example:
// var b = new BrowserInfo();
// alert(b.version);
function BrowserInfo()
{
this.name = navigator.appName;
this.codename = navigator.appCodeName;
this.version = navigator.appVersion.substring(0,4);
this.platform = navigator.platform;
this.javaEnabled = navigator.javaEnabled();
this.screenWidth = screen.width;
this.screenHeight = screen.height;
}
------------------------------
<!--
function sizeRedirect()
{
var wide = window.screen.width;
if(wide = 800) URLStr = "1.html";
else URLStr = "2.html";
location = URLStr;
}
//-->
-------------------------------------
</script>
</head>
<body onLoad="ANY_FUNCTION_NAME_ABOVE_THAT_YOU_LIKE()">
==============================================
there u go...mix and match for whatever version/need u have
All the best!