How to add CSS
CSS is added to HTML pages to format the document according to information in the style sheet. There are three ways to insert CSS in HTML documents.
1) Inline CSS
Inline CSS is used to apply CSS on a single line or element.
For more visit here: Inline CSS
2) Internal CSS
Internal CSS is used to apply CSS on a single document or page. It can affect all the elements of the page. It is written inside the style tag within head section of html.
For more visit here: Internal CSS
3) External CSS
External CSS is used to apply CSS on multiple pages or all pages. Here, we write all the CSS code in a css file. Its extension must be .css for example style.css.
You need to link this style.css file to your html pages like this:
The link tag must be used inside head section of html.
For more visit here: External CSS