<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
/* For device width smaller than 400px: */
body {
background-repeat: no-repeat;
background-image: url('img_smallflower.jpg');
}
/* For device width 400px and larger: */
@media only screen and (min-device-width: 400px) {
body {
background-image: url('img_flowers.jpg');
}
}
</style>
</head>
<body>
</body>
</html>