CSS - Cascading Style Sheet

Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language such as HTML or XML (including XML dialects such as SVG, MathML or XHTML). CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.

To use CSS with HTML document, there are three ways:

Inline CSS: Define CSS properties using style attribute in the HTML elements.
Internal or Embedded CSS: Define CSS using <style> tag in <head> section.
External CSS: Define all CSS property in a separate .css file, and then include the file with HTML file using tag in section.

<!DOCTYPE HTMl>

<html>

<head>

<style>

.intro{text-align:center;color:blue}

</style>

</head>

<body>

<h1 class="intro">this heading is blue and center-aligned.</h1>

<p class="intro">this paragraph is blue and center-aligned.</p>

</body>

</html>

Output -:

this heading is blue and center-aligned.

this paragraph is blue and center-aligned.