What is the Difference Between HTML and CSS?

Source code showing the difference between HTML and CSS side-by-side. — Code View of HTML and CSS
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Building a website requires understanding two fundamental technologies: HTML and CSS. Both are essential for creating web pages, but they serve very different purposes. This guide will explain the differences between HTML and CSS, and how they work together to build and style website content.

What is HTML?

HTML (HyperText Markup Language) is the standard language used to create the structure of a webpage. It defines the page's content, such as headings, paragraphs, images, links, and other elements.

The basic building blocks of HTML are tags, which define the different types of content on a page. Each tag usually comes in pairs: an opening tag (<p>) and a closing tag (</p>), with the content placed between them.

Example: A Simple HTML Structure


<!DOCTYPE html>
<html>
  <head>
    <title>My First Website</title>
  </head>
  <body>
    <h1>Welcome to My Website</h1>
    <p>This is a paragraph of text on my website.</p>
  </body>
</html>

What is CSS?

CSS (Cascading Style Sheets) is the language used to describe the visual presentation of a webpage. While HTML provides the structure, CSS is responsible for the design and layout. It allows you to control the colors, fonts, spacing, and overall appearance of your website.

CSS uses selectors to target HTML elements and apply styles to them. Each style is defined by a property (such as color or font-size) and a value (such as blue or 16px).

Example: A Simple CSS Rule


p {
  color: blue;
  font-size: 16px;
}

HTML and CSS: How They Work Together

HTML and CSS are designed to complement each other. HTML defines the structure of a webpage, while CSS defines the styles for that structure.

There are three ways to include CSS in an HTML document:

Inline styles: Directly inside the HTML element using the style attribute.
Internal styles: Inside a <style> tag within the <head> of the HTML document.
External stylesheets: In a separate CSS file linked to the HTML document.

Let's take a closer look at each of these three methods for including CSS in your HTML document, with an example for each approach.

Example: Inline Style Attribute


<p style="font-weight: bold; color: red;">This text is bold and red.</p>

Example: Internal Styles Within Head


<head>
  <style>
    p {
      font-size: 18px;
      color: green;
    }
  </style>
</head>
<body>
  <p>This text is 18px and green.</p>
</body>

Example: External CSS File Link Within Head


<head>
  <link rel="stylesheet" href="styles.css">
</head>

Differences Between HTML and CSS

While HTML and CSS are often used together, they have distinct roles:

HTML is responsible for the structure of the webpage, determining what content appears and in what order.
CSS is responsible for the style of the webpage, determining how the content looks, including colors, fonts, and layout.
HTML uses tags to define elements, while CSS uses selectors to apply styles to those elements.

Keeping structure (HTML) and style (CSS) separate allows for cleaner code and easier maintenance. For example, you can change the entire appearance of a website by updating a single CSS file, without altering the HTML.

Example: Combining HTML and CSS


<!DOCTYPE html>
<html>
  <head>
    <link rel="stylesheet" href="styles.css">
  </head>
  <body>
    <h1>Welcome to My Website</h1>
    <p>This is a paragraph.</p>
  </body>
</html>

Common Mistakes Beginners Make

It's common for beginners to mix HTML and CSS, which can lead to messy and difficult-to-maintain code.

Here are a few mistakes to avoid:

Using inline styles excessively instead of external CSS.
Not keeping HTML structure clean and CSS styles organized.
Not using proper CSS selectors to target elements.

Correcting these Mistakes

It's best to use an external CSS file to keep HTML and CSS separate and well-organized. This makes your code more maintainable and efficient.

Best Practices for Using HTML and CSS Together

To write clean, efficient code, follow these best practices:

Use semantic HTML to ensure your website's structure is meaningful.
Organize your CSS using classes and IDs, and avoid using overly specific selectors.
Keep your HTML free of inline styles and unnecessary attributes.

Following these guidelines will make your website easier to manage and improve its performance.

Final Thoughts

In summary, HTML and CSS work together to build and style websites, but they have very different roles. HTML provides the structure, while CSS defines the presentation. By understanding the difference between them, you can create clean, well-organized websites that are easy to maintain and update.

CSS Code

Resources:

The Head Element. HTML Living Standard. Retrieved October 6, 2024.
Attributes. Web.dev. Retrieved October 6, 2024.
Difference between HTML and CSS. Geeks for Geeks. Retrieved October 6, 2024.
Starting with HTML + CSS. The World Wide Web Consortium (W3C). Retrieved October 6, 2024.
CSS Basics. Mozilla. Retrieved October 6, 2024.
Cascading Style Sheets (CSS). WIKIPEDIA. Retrieved October 6, 2024.
HTML Styles - CSS. W3Schools. Retrieved October 6, 2024.

Code View of HTML and CSS