To add CSS (Cascading Style Sheets) to your HTML document, you can use the `<style>` tag within the `<head>` section of your HTML file. Here's a simple example:
1. Create an HTML file (e.g., index.html) and open it in a text editor.
2. Inside the `<head>` section of your HTML file, add a `<style>` tag.
3. Within the `<style>` tag, write your CSS code. For example:
```html
<!DOCTYPE html>
<html>
<head>
<title>My Web Page</title>
<style>
body {
font-family: Arial, sans-serif;
background-color: #f0f0f0;
color: #333;
}
h1 {
color: #007bff;
}
p {
font-size: 16px;
}
/* Add more CSS rules as needed */
</style>
</head>
<body>
<h1>Hello, world!</h1>
<p>This is a sample paragraph.</p>
</body>
</html>
```
4. Save the HTML file and open it in a web browser to see the CSS styles applied to the content.
This is a basic example of adding CSS to an HTML file. You can apply various CSS properties to different HTML elements by selecting them using tags, classes, or IDs in your CSS code. CSS allows you to control the layout, appearance, and styling of your web page elements.
