[html] How to center horizontal table-cell

Short snippet for future visitors - how to center horizontal table-cell (+ vertically)

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html, body {_x000D_
  width: 100%;_x000D_
  height: 100%;_x000D_
}_x000D_
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.tab {_x000D_
  display: table;_x000D_
  width: 100%;_x000D_
  height: 100%;_x000D_
}_x000D_
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.cell {_x000D_
  display: table-cell;_x000D_
  vertical-align: middle;_x000D_
  text-align: center; /* the key */_x000D_
  background-color: #EEEEEE;_x000D_
}_x000D_
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.content {_x000D_
  display: inline-block; /* important !! */_x000D_
  width: 100px;_x000D_
  background-color: #00FF00;_x000D_
}
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<div class="tab">_x000D_
  <div class="cell">_x000D_
    <div class="content" id="a">_x000D_
      <p>Content</p>_x000D_
    </div>_x000D_
  </div>_x000D_
</div>
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