its just only in mobile mode, i don’t know to remove this, purple line is from background.
<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>layout</title>
<style>
body {
background-color: blueviolet;
}
header, main, footer {
background-color: #fff;
}
h1,h2,p {
margin: 0;
padding: 0;
}
</style>
</head>
<body>
<header>
<h1>this is header</h1>
</header>
<main>
<h2>this is main</h2>
</main>
<footer>
<p>this is footer</p>
</footer>
</body>