小编Rek*_*ha 的帖子

div#div1 {
  position: absolute;
  left: 0;
  right: 0;
  height: 100px;
  border: 1px solid green;
  background-color: green;
  width: 100%;
}

td {
  position: relative;
  border: 1px solid blue;
  height: 18px;
  width: 100%;
}

table {
  width: 100%;
}

<table>
  <tr>
    <td>
      <div id="div1">
        This is a heading with an absolute position
      </div>
    </td>
  </tr>
</table>

body {
  height: 200px;
  background-color: lightblue;
  padding: 0px;
  border: 1px solid red;
}

<html>

<head>
</head>

<body>
  <p> First para </p>
  <p> Second para </p>

</body>

</html>