files/zh-tw/web/css/_colon_first-child/index.html


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---
title: ':first-child'
slug: 'Web/CSS/:first-child'
tags:
  - CSS
  - CSS Pseudo-class
  - Layout
  - Reference
  - Web
translation_of: 'Web/CSS/:first-child'
---
<div>{{CSSRef}}</div>

<p><code>:first-child</code>是<a href="/en-US/docs/Web/CSS">CSS</a>當中的一種<a href="/en-US/docs/Web/CSS/Pseudo-classes">偽類別（pseudo-class）</a>，代表任何身為長子的元素（親元素的第一個子元素）。</p>

<h2 id="語法">語法</h2>

<pre class="syntaxbox">{{csssyntax}}
</pre>

<h2 id="範例">範例</h2>

<h3 id="範例_1">範例 1</h3>

<h4 id="HTML_內文">HTML 內文</h4>

<pre class="brush: html">&lt;div&gt;
  &lt;span&gt;This span is limed!&lt;/span&gt;
  &lt;span&gt;This span is not. :(&lt;/span&gt;
&lt;/div&gt;
</pre>

<h4 id="CSS_內文">CSS 內文</h4>

<pre class="brush: css">span:first-child {
    background-color: lime;
}
</pre>

<p>呈現效果如下：</p>

<p><span>{{EmbedLiveSample('範例_1',300,50)}}</span></p>

<h3 id="範例_2_-_使用_UL">範例 2 - 使用 UL</h3>

<h4 id="HTML_內文_2">HTML 內文</h4>

<pre class="brush: html">&lt;ul&gt;
  &lt;li&gt;List 1&lt;/li&gt;
  &lt;li&gt;List 2&lt;/li&gt;
  &lt;li&gt;List 3&lt;/li&gt;
&lt;/ul&gt;</pre>

<h4 id="CSS_內文_2">CSS 內文</h4>

<pre class="brush: css">li{
  color:red;
}
li:first-child{
  color:green;
}</pre>

<p>呈現效果如下：</p>

<p><span>{{EmbedLiveSample('範例_2_-_使用_UL',300,100)}}</span></p>

<h2 id="規格">規格</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">規格</th>
   <th scope="col">狀態</th>
   <th scope="col">註解</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{SpecName('CSS4 Selectors', '#first-child-pseudo', ':first-child')}}</td>
   <td>{{Spec2('CSS4 Selectors')}}</td>
   <td>無變更</td>
  </tr>
  <tr>
   <td>{{SpecName('CSS3 Selectors', '#first-child-pseudo', ':first-child')}}</td>
   <td>{{Spec2('CSS3 Selectors')}}</td>
   <td>無變更</td>
  </tr>
  <tr>
   <td>{{SpecName('CSS2.1', 'selector.html#first-child', ':first-child')}}</td>
   <td>{{Spec2('CSS2.1')}}</td>
   <td>初始定義</td>
  </tr>
 </tbody>
</table>

<h2 id="瀏覽器相容性">瀏覽器相容性</h2>

<p>{{CompatibilityTable}}</p>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>功能</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>基礎支援</td>
   <td>4.0</td>
   <td>{{CompatGeckoDesktop("1.9")}}</td>
   <td>7<sup>[1]</sup></td>
   <td>9.5</td>
   <td>4</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>功能</th>
   <th>Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>基礎支援</td>
   <td>1.0</td>
   <td>{{CompatGeckoMobile("1.9.1")}}</td>
   <td>7<sup>[1]</sup></td>
   <td>10.0</td>
   <td>3.1</td>
  </tr>
 </tbody>
</table>
</div>

<p>[1] 在不重新載入網頁的情況下，Internet Explorer 7 的樣式表並不會套用在動態新增的元素上。在 Internet Explorer 8，若元素是以點擊連結而形成的，則 <code>first-child</code> 在該連結不被選取後才有作用。</p>

<h2 id="參見">參見</h2>

<ul>
 <li>{{cssxref(":last-child")}}</li>
 <li>{{cssxref(":nth-child")}}</li>
 <li>{{cssxref(":last-of-type")}}</li>
</ul>