JSDG 13.6

<script type="text/javascript">
/*@cc_on
  @if (@_jscript)
    // 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
    // except IE will run this code.
    alert('You are not using Internet Explorer');
/*@end
  @*/
</script>

 按理说这是IE中javascript条件注释。

以/*@cc_on 开头，@*/结束的。而且JScript是Microsoft自己的JavaScript解释器的名字，而@_jscript变量在IE中为True。

但我在IE7中，似乎认不到条件注释。

firefox却可以。不知道是IE版本不对，还是怎么回事。

来源：https://www.cnblogs.com/rorodo/archive/2012/08/23/2651871.html