<!DOCTYPE html>
<html style="background-color: blue;">
<body style="margin:0;">
<div style="background-color: green; width: 25vw; height: 25px;"></div>
</body>
</html>
<!DOCTYPE html>
<html style="background-color: blue;">
<body style="margin:0;">
<div style="background-color: green; width: 25vw; height: 25px;"></div>
</body>
</html>