What is CSS?

Learn what CSS is, how it differs from HTML, and how it styles a page.

What is CSS?

CSS stands for Cascading Style Sheets. It is not a programming language, it is a styling language. Its job is to describe how an HTML page should look: colors, fonts, spacing, layout.

The browser reads the HTML, applies the CSS declarations it finds, and draws the result on screen. The same HTML document can look completely different with different CSS.

HTML structure, CSS style

HTML builds the structure of the page: headings, paragraphs, links, images. CSS decides the style of that same page: color, size, alignment, spacing.

For example, the body tag wraps the whole page. With CSS you give the body selector a color, and the whole page picks it up. This split lets you keep two files: HTML for content, CSS for appearance.

The stylesheet

CSS declarations together form a stylesheet. It is a plain text file ending in .css; it holds rows of selectors and declarations.

A single stylesheet can style hundreds of pages. Change the file once, and every page on the site updates at the same time. This makes it easy to keep a site consistent.

Exercise Set a color for body

Write a body selector and add a color: #333 declaration inside. This makes all text on the page dark gray.

Show example solution

/* add the body style */
body {
  color: #333;
}

Test yourself

What does CSS determine?
```
body {
  color: navy;
  font-family: sans-serif;
}
```
- The structure and content of the page
- Data exchange with the server
- The appearance and styling of the page
- Database queries
Show answer

The appearance and styling of the page — Correct. CSS determines style properties like color, font and spacing.
Match each term to its meaning

CSS

Styling language
HTML

Markup language
Stylesheet

.css file
Browser

Draws code on screen

Select the page body

____ {
  color: #333;
  line-height: 1.5;
}

Show answer

body {
  color: #333;
  line-height: 1.5;
}

Next lesson: Linking CSS to HTML

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