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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

              <div class="content">
  <p class="p">CSS 否定伪类选择器 <em>:not(X)</em>,是以一个简单的以选择器 `X` 为参数的功能性标记函数,将从匹配的元素集合中排除选择器 `X` 所匹配的元素。选择器 `X` 中不能包含另外一个 <em>:not()</em> 选择器。</p>

  <div class="notice"><em>:not()</em> 伪类可以将一个或多个以逗号分隔的选择器作为其参数。但是以多个以逗号分隔的选择器作为参数是实验性的,尚未广泛支持。</div>

  <p class="p"><em>:not()</em> 伪类时我们得选择器组合更加灵活,我们来看一些简单的应用</p>
              .content :not(.notice) em{
.content .notice{ 
     background: #ffe7e8;
    border-left: 4px #e66465 solid;
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