If you want to learn frontend web development, there are always two languages that come up right in your mind: HTML and CSS. As the core languages of a site’s client-side, HTML and CSS have distinct roles that work together. It’s important to understand them individually and how they collaborate to organize and design a website productively. So, in this article, we will talk about the main difference between HTML and CSS and how they play a crucial part in making a smooth website as well.

Before diving into the differences between HTML and CSS, we need to explore the definition of each language first.
HTML stands for HyperText Markup Language. It’s the core language behind building web pages. With this in mind, its primary purpose is to define the structure and content of the web page. In a simple metaphor, HTML is like the frame of a house, showing you where everything (e.g., rooms, walls, doors) is and how to get around the building.
To achieve this goal, HTML uses a system of HTML elements, also known as “tags.” These tags contain special characters that represent the content they mark up and are enclosed in angle brackets (e.g., <title>). There are various tags used to create elements like headings, paragraphs, images, lists, links, etc.
By arranging all the content in different tags within an HTML document, a web browser can understand and display the content clearly. This helps site visitors capture key information and navigate easily through a web page. Also, it allows search engine crawlers to index the page through keywords, links, and more easily, making your site easily reach the top ranking on the results page.
Below is a simple example of how HTML looks in practice:

In this example, each part of the content (e.g., Heading 1) contains a start tag (<h1>), element content (Welcome!), and an end tag (</h1>).
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CSS is an abbreviation for Cascading Style Sheets. If HTML creates the structure and content for your web page, CSS makes that structure colorful and lively by defining how HTML elements should look on the page. In other words, it’s primarily responsible for controlling the page’s presentation and styling.
CSS creates all visual elements of a web page, from the most fundamental ones (e.g., fonts, text sizes, colors) to more complex aspects (e.g., layout, spacing, animations). This style sheet language even defines how a website is responsive across different screen sizes. Without CSS, your web pages, albeit functional, look plain and visually unappealing.
So, how can CSS style an HTML document? Let’s take a look at an example below:

CSS’s fundamental syntax often includes the following three factors:
As you can see, CSS has a straightforward syntax to help developers accurately control the visual appeal of every HTML element. Accordingly, each property-value pair is separated by a semicolon (:). And in each selector, a set of these pairs is enclosed by curly braces { }.
HTML and CSS are indispensable parts of frontend web development, although their core goal and functions are technically different. Here’s a table summarizing the key differences between HTML and CSS:
| Feature | HTML | CSS |
| Purpose and Role | Defines the structure and content of a web page | Identifies the styling and presentation of a web page |
| Syntax | Uses tags (like <h1>, <p>, <img>) and attributes (like src, alt) For example: <h1> Designveloper </h1> |
Utilizes selectors, properties, and values
For example: h1 { font-family: georgia } |
| File Extension | .html or .htm | .css |
| Independence | Can run independently without CSS, although the output will look unstyled and unattractive | Can’t exist independently without HTML |
Despite their key differences, HTML and CSS still share similarities that turn them into an inseparable pair in frontend web development. Below are several common characteristics you may find in these two languages:
1. Both are crucial for modern web development. HTML and CSS are the second most commonly used languages, with nearly 53% of users worldwide. They’re integral materials to create a functional, visually pleasing, and user-friendly website.
2. Both are written in plain text files. This means developers can leverage any simple text editor to create and edit their code. For this reason, both HTML and CSS are highly accessible for not only developers but also non-technical users to write their code without specialized compilation software.
3. All web browsers can interpret HTML and CSS. Whether you use Chrome, Safari, or Firefox, your web browser can read and interpret HTML/CSS files easily. This allows the browser to display web pages exactly as you intended.
Although HTML and CSS serve different purposes, they often work together to create visually rich and interactive web experiences.
As we already said, HTML can exist independently without the integration of CSS. But HTML-only web pages often look boring and unappealing, hence making it hard to attract and retain your potential customers. This will make your site a big disadvantage for your company, especially in this competitive landscape.
So, the combination of HTML and CSS is a must to at least ensure an engaging, functional website. It’s like when you build a house (“website”) with a firm structure (HTML) and aesthetic details (CSS) to make the building livable and beautiful.
There are many ways to apply CSS to HTML documents. They include: Inline styles, Internal stylesheets, and External stylesheets.
This method involves using CSS code directly in individual HTML elements. It can be done by leveraging the style attribute. Let’s take a look at the code and the output below:

Pros: Very fast for small, one-off changes
Cons: Inline styles shouldn’t be used for general cases. As you can see, this approach mixes content (HTML) and presentation (CSS). This makes it hard for developers to read, maintain, and update the code across a large website.
This method inserts CSS in the <style> tag in the <head> section of an HTML document. Let’s see an example of the code and the output as follows:

Pros: Internal stylesheets are useful if you want to adopt unique styles to a single HTML page and don’t use these styles elsewhere.
Cons: This method still mixes some CSS into the HTML document. If you have various pages, you need to copy and paste the same styles into the <head> section of each page. This makes site-wide changes difficult and time-wasting.
This approach links separate .css files to the HTML document through the <link> tag in the <head> section. Below is the code of the eternal stylesheets:
For HTML files:

For external CSS files:
h1 {
color: blue;
font-family: Arial, san-serif;
}
p {
line-height: 1.5;
}
Note: As there’s no real CSS file attached to this HTML document, the output isn’t displayed in the expected way. However, external stylesheets are the best way to apply CSS to HTML documents for several reasons:
After this article, we expect you to have a better understanding of the key differences between HTML and CSS. Further, you may understand the importance of these two languages and how to apply CSS to HTML documents to create a site. Wanna learn more about HTML, CSS, and other languages like JavaScript to build a seamless frontend for your site? Subscribe to our blog and receive the latest posts about them!