1. Inline CSS: This is the simplest way to apply CSS to a web page. With inline CSS, you apply the style directly to the HTML element using the style attribute and CSS declarations. For example:

This is a heading

2. Internal or Embedded CSS: Internal CSS is used when you want to apply a unique style to a single HTML page. You can define internal CSS in the section of an HTML page, by using the tag. For example:

h1 {
color: blue;
font-size: 24px;
}

3. External CSS: External CSS is used when you want to apply the same style to multiple HTML pages. You can link to an external CSS file using the tag. For example: