I have this HTML and this CSS but when I update the browser, there is no change
<style>
#a {
width: 100px;
height: 100px;
color: red;
}
</style><html lang="es">
<head>
<meta charset="utf-8"/>
<title>Proyecto</title>
<link rel="stylesheet" type="text/css" href="123.css">
</head>
<body>
<header>
<li id="a">Hola</li>
</header>
</body>
</html> If you have a .css file, you do not have to indicate the <style> tags. They are html tags.
#a {
width: 100px;
height: 100px;
color: red;
}
<html lang="es">
<head>
<meta charset="utf-8"/>
<title>Proyecto</title>
<link rel="stylesheet" type="text/css" href="123.css">
</head>
<body>
<header>
<li id="a">Hola</li>
</header>
</body>
</html>