External CSS #
Use the <link> element in the <head> element.
This way is used a lot.
<head>
<link rel="stylesheet" href="path" />
</head>body {
background-color: gray;
}Internal CSS #
Use the <style> element in the <head> element.
<head>
<style>
body {
background-color: gray;
}
</style>
</head>Inline CSS #
Use the <style> attribute.
<body style="background-color: gray"></body>