title: Why is the span's line-height useless?
body: <p>First, let's see a piece of code:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>div { width:200px; height:200px; border:1px solid black; line-height:200px; }
  span { line-height:1.7;  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div&gt;&lt;span&gt;123&lt;br&gt;456&lt;br&gt;789&lt;br&gt;000&lt;/span&gt;&lt;/div&gt;</code></pre>
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  </p>
  
  <p>Why is the <code>span</code>'s <code>line-height</code> unused?</p>
  
  <p>The <code>line-height</code> is still <code>200px</code>, but when we set <code>span</code>'s <code>display</code> property to <code>inline-block</code>, the <code>line-height</code> of the <code>span</code> is used?</p>
  
  <p>See below:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>div { width:200px; height:200px; border:1px solid black; line-height:200px; }
  span { display:inline-block; line-height:1.7; }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div&gt;&lt;span&gt;123&lt;br&gt;456&lt;br&gt;789&lt;br&gt;000&lt;/span&gt;</code></pre>
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  </p>