我们常常会在网页的HTML里面看到形如[if lte IE 9]……[endif]的代码，表示的是限定某些浏览器版本才能执行的语句，那么这些判断语句的规则是什么呢？请看下文：
注意：以下用法不支持IE10和IE11
<!--[if !IE]><!--> 除IE外都可识别（不是IE） <!--<![endif]-->
<!--[if IE]> 所有的IE可识别 <![endif]-->
<!--[if IE 6]> 仅IE6可识别 <![endif]-->
<!--[if lt IE 6]> IE6以及IE6以下版本可识别 <![endif]-->
<!--[if gte IE 6]> IE6以及IE6以上版本可识别 <![endif]-->
<!--[if IE 7]> 仅IE7可识别 <![endif]-->
<!--[if lt IE 7]> IE7以及IE7以下版本可识别 <![endif]-->
<!--[if gte IE 7]> IE7以及IE7以上版本可识别 <![endif]-->
<!--[if IE 8]> 仅IE8可识别 <![endif]-->
<!--[if IE 9]> 仅IE9可识别 <![endif]-->
| 项目 | 范例 | 说明 |
|---|---|---|
| ! | <!--[if !IE]><!--> |
The NOT operator. This is placed immediately in front of the feature, operator, or subexpression to reverse the Boolean meaning of the expression. |
| lt | [if lt IE 5.5] |
The less-than operator. Returns true if the first argument is less than the second argument. |
| lte | [if lte IE 6] |
The less-than or equal operator. Returns true if the first argument is less than or equal to the second argument. |
| gt | [if gt IE 5] |
The greater-than operator. Returns true if the first argument is greater than the second argument. |
| gte | [if gte IE 7] |
The greater-than or equal operator. Returns true if the first argument is greater than or equal to the second argument. |
| ( ) | [if !(IE 7)] |
Subexpression operators. Used in conjunction with boolean operators to create more complex expressions. |
| & | [if (gt IE 5)&(lt IE 7)] |
The AND operator. Returns true if all subexpressions evaluate to true. |
| | | [if (IE 6)|(IE 7)] |
The OR operator. Returns true if any of the subexpressions evaluates to true. |
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