少了空格多了0
<input type=button id=B2 value=go onclick=alert(navigator.appVersion)>
<script>B2.disabled = (navigator.appVersion.indexOf("MSIE 6.")==-1);</script>
<input type=button id=B2 value=go onclick=alert(navigator.appVersion)>
<script>B2.disabled = (navigator.appVersion.indexOf("MSIE 6.")==-1);</script>
|| navigator.appVersion.indexOf("MSIE 4") != -1
|| navigator.appVersion.indexOf("MSIE 5") != -1)
{
B2.disabled = true;
}
else
{
B2.disabled = false;
}