Just spent 30 seconds whipping up some javascript to support Tim Bray’s Use A Better Browser idea.

<pre class="code">
<script type="text/javascript" language="javascript">
<!--
function betterBrowser (){
    var agt=navigator.userAgent.toLowerCase();
    var is<em>major = parseInt(navigator.appVersion);
    var is</em>minor = parseFloat(navigator.appVersion);

<code>var is_nav  = ((agt.indexOf('mozilla')!=-1) &amp;&amp; (agt.indexOf('spoofer')==-1)
    && (agt.indexOf('compatible') == -1) &amp;&amp; (agt.indexOf('opera')==-1)
    && (agt.indexOf('webtv')==-1) &amp;&amp; (agt.indexOf('hotjava')==-1));

var is_ie  = ((agt.indexOf("msie") != -1) &amp;&amp; (agt.indexOf("opera") == -1));

if ( ( is_nav &amp;&amp; is_major &lt; 5 ) || is_ie ) {
    document.write('&lt;a href="http://www.tbray.org/ongoing/When/200x/2003/07/17/BrowserDream"&gt;');
        document.write('&lt;img src="http://laughingmeme.org/betterbrowser.gif" border="0"&gt;&lt;/a&gt;');
}
</code>

<p>}
//-->
</p>