Simple CSS code inside <style> tag or in an external css file which leads to incorrect rendering

[altagore]

Hello all,
When I put CSS code in a <style> tag to put a border around a div element, below my div block appear three borders nested inside each other. I have the same problem if I put the CSS code in an external file. Please note that I use Chrome as my browser.

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<style>
div {
border: 1px solid red;
background-color: antiquewhite;
left: 10px; margin: 10px
}
</style>
</head>
<body>
<div>Bloc div</div>
</body>
</html>

A copy of the result is shown below:

If, on the other hand, I directly put my CSS code by assigning it to the style attribute of the div element, I no longer have this problem.
I have the same problem with Ritwick Dey's Live server extension and with the Live Server (Five Server) extension.
I would like to point out that when I open my file directly with the browser, all is ok.
Thanks for your help