> For the complete documentation index, see [llms.txt](https://shsbt.gitbook.io/hack-the-web/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shsbt.gitbook.io/hack-the-web/build-with-the-basics/css.md).
# CSS
CSS (Cascading Style Sheets) is a language used to control the appearance and layout of web pages. While HTML defines the structure of a webpage (like headings, paragraphs, and links), CSS is used to make it look nice by controlling things like colors, fonts, and spacing.
### How CSS Works:
CSS is made up of **rules** that tell the browser how to style elements of the page. Each rule has two parts:
1. **Selector**: The part of the page you want to style (like a heading or paragraph).
2. **Declarations**: The styles you want to apply, written inside curly braces `{}`. Each declaration has a **property** (like color) and a **value** (like red).
#### Example of CSS:
```html
Hello, world!
This is my first styled web page.
```
#### Breaking It Down:
* **`body { background-color: lightblue; }`**: This changes the background color of the entire webpage to light blue.
* **`h1 { color: navy; font-size: 36px; }`**: This makes the heading (`h1`) text dark blue and larger in size.
* **`p { font-family: Arial, sans-serif; color: darkgray; }`**: This changes the font of the paragraph to Arial and makes the text color dark gray.
#### CSS can be added to a web page in 3 ways:
1. **Inline CSS**: Styles are added directly within HTML tags. Example: `This is a paragraph.
`.
2. **Internal CSS**: Styles are included within a `