ID 选择器

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

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CSS ID 选择器会根据该元素的 id 属性中的内容匹配元素。为了使该元素被选中，它的 id 属性必须与选择器中给出的值完全匹配。

css

/* id 为 "demo" 的元素会被选中 */
#demo {
  border: red 2px solid;
}

语法

css

#id 属性值 { 样式声明 }

它与下面的属性选择器语句语法上等价（但优先级并不等价）：

css

[id=id 属性值] { 样式声明 }

css

#identified {
  background-color: skyblue;
}

html

<div id="identified">这个 div 有一个特别的 ID 属性！</div>
<div>这只是一个普通的 div。</div>

Specification
Selectors Level 4 # id-selectors

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