<!--[if IE]>
This content is actually inside an HTML comment.
It will only be displayed in IE.
<![endif--]>
<!--[if IE6]>
This content is actually only be displayed by IE 6 and later.
<![endif]-->
<!--[if !IE]><-->
This is normal HTML content,but IE will not display it because of
the comment above and the comment below.
<!--><![endif]-->
This is normal content,displayed by all browsers.
<script>
/*@cc_on
@if(@_jscript)
//This code is inside a JS comment but is executed in IE.
//This code is inside a conditional comment,which is also a
//regular Javascript comment.IE runs it but other browsers ignore it.
alert("You are using Internet Explorer");
@else*/
//This code is no longer inside a Javascript comment,but is still
//inside the IE conditional comment. This means that all browsers
//excepte IE will run this code.
alert("you are not using Internet Explorer");
/*@end
@*/
</script>
有些用处，但非标准。