How to make a very simple web page with just a dynamic image—nothing else.

meaghanm60433811  wrote I just want to build a web site with a JPEG in the background that will look proportional on mobile devices and desktops. No text, no links—nothing except the image.

No content means it's invisible to search engines, screen readers and language translators.  Apart from the obvious accessibility problems,  a lack of real HTML content = no traffic to your website except what you pay for in keyword ads. 

Copy & paste this code into a new, blank document in Code View.

SaveAs test.html and preview in browsers and mobile devices.

<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Background-Size Cover Demo</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<style>
body, html {
margin: 0;
padding: 0;
height: 100%;
display: flex;
align-items: center;
justify-content: center;
}
body {
background: url(https://placeimg.com/900/900/nature) center center fixed;
background-size: cover
}
.container {
width: 40%;
margin: 0 auto;
padding: 5%;
background: rgba(255,255,255,0.8);
}
.center { text-align: center }
</style>
</head>
<body>
<div class="container">
<h2>Heading 2</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
<p class="center"><a href="https://example.com" class="button">CLICK HERE</a></p>
</div>
</body>
</html>