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CSS
HTML
Result

.ex1 {
  -moz-tab-size: 4; /* Firefox */
  -o-tab-size: 4; /* Opera 10.6*/
  tab-size: 4;
}

.ex2 {
  -moz-tab-size: 8; /* Firefox */
  -o-tab-size: 8; /* Opera 10.6 */
  tab-size: 8;
}

.ex3 {
  -moz-tab-size: 12; /* Firefox */
  -o-tab-size: 12; /* Opera 10.6 */
  tab-size: 12;
}

<!DOCTYPE html>
<html lang="ko">
  <head></head>
  <body>
    <h1>tab-size</h1>
    <pre class="ex1">I	use	tab-size	4</pre>
    <pre class="ex2">I	use	tab-size	8</pre>
    <pre class="ex3">I	use	tab-size	12</pre>
  </body>
</html>