<!DOCTYPE html>
<html>
<title>W3.CSS</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://www.w3schools.cn/w3css/4/w3.css">
<body>
<button class="w3-button w3-red" onclick="document.getElementById('id01').style.display='block'">显示面板</button>
<div id="id01" class="w3-panel w3-green w3-display-container" style="display:none">
<span onclick="this.parentElement.style.display='none'"
class="w3-button w3-red w3-display-topright">x</span>
<p>单击 X 关闭此面板。</p>
<p>单击 X 关闭此面板。</p>
</div>
</body>
</html>