Detect Internet Explorer

<script type="text/javascript">
    if (/MSIE (\d+\.\d+);/.test(navigator.userAgent)) {
//test for MSIE x.x;
        var ieversion = new Number(RegExp.$1)
// capture x.x portion and store as a number
        if (ieversion >= 8)
            document.write("You're using IE8 or above")
        else if (ieversion >= 7)
            document.write("You're using IE7.x")
        else if (ieversion >= 6)
            document.write("You're using IE6.x")
        else if (ieversion >= 5)
            document.write("You're using IE5.x")
    } else
        document.write("n/a")
</script>