CSS Tutorial

External CSS is the most recommended and professional method for styling web pages. With this method, all styles are written in a separate file with the extension .css, which the HTML document links using the <link> tag in the page header.

EXAMPLE

                        <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>External CSS Example</title>
    <link rel="stylesheet" href="style.css">
</head>
<body>
    <h1>Example of Using External CSS</h1>
    <div class="box">
        <p>This paragraph is styled using the styles written in a separate file style.css.</p>
        <p>If you want to change the appearance of this page, open the file style.css and change the code there. The 
        change will apply to all pages using this file.</p>
    </div>
</body>
</html>
                    

RESULT

How Does It Work?

Imagine you have a large house with 10 rooms (web pages). Instead of writing styling rules on the wall of each room separately (Internal CSS) or on every piece of furniture (Inline CSS), you write one rulebook (CSS file) and place it in the hallway. All rooms (pages) reference this book. If you want to change the wall color in all rooms, you only change the book once, and the change applies to the entire house.

Why Is This the Best Method?

Code Reusability: One CSS file can style 100 different pages. If you change one line in the CSS file, the change is immediately reflected on all pages.
Loading Speed (Cache): The browser loads the CSS file once and stores it in memory (cache). When a user visits another page on your website, the browser does not load the CSS again, which speeds up performance.
Clean Code: HTML files are clean and readable, as they do not contain long style definitions. Separation of content (HTML) and presentation (CSS) is the foundation of modern web development.
Easier Maintenance: When you want to change the design of the entire site, you only open one file, not 50 HTML files.

When to Use?

External CSS is mandatory for:

All large websites and online stores.
Websites with more than 3-5 subpages.
Projects where multiple people collaborate on development.
Websites that want high speed and good SEO ranking.

Conclusion: If you want to create a professional, fast and easy-to-maintain website, External CSS is the only right choice. Use Inline and Internal CSS only for quick tests or very small projects.