Background: I have been looking at some interview questions recently, and there are some solutions about horizontal and vertical centralization. I usually use Flex, and seldom use table-cell

If you really want to achieve vertical centering, table-cell alone is not enough

  1. Table-cell The width and height need to be set
  2. The child elements of the table-cell must bedisplay: inline-block;Cannot be block-level elements
<! DOCTYPEhtml>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="Width = device - width, initial - scale = 1.0">
    <title>Document</title>
    <style>
        #id1 {
            width: 100px;
            height: 100px;
            background: blue;
            display: table-cell;
            vertical-align: middle;
            text-align: center;
        }
        #id2 {
            background: red;
            display: inline-block;
            width: 50%;
            height: 50%;
        }
    </style>
</head>
<body>
    <div id="id2">
        <div id="id3">Test the</div>
    </div>
</body>
</html>
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