HTML Core Concepts

HyperText Markup Language fundamentals and document structure

What is HTML?

HyperText Markup Language (HTML) is the standard markup language for structuring web content. It defines the meaning and structure of content using elements represented by tags.

html

// Basic HTML Document
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>My Page</title>
  </head>
  <body>
    <h1>Hello World</h1>
    <p>Welcome to my website.</p>
  </body>
</html>

How HTML Works

HTML Request → Render Flow

Interview Q&A

💬 What does DOCTYPE do?

<!DOCTYPE html> tells the browser to use HTML5 standards mode. Without it, browsers may use 'quirks mode' which emulates legacy behavior and can cause inconsistent rendering.

💬 Difference between HTML and XHTML?

XHTML is stricter — all tags must be closed, lowercase, and properly nested. HTML5 is more forgiving. XHTML uses XML syntax rules while HTML5 uses its own parser.

💬 What is the DOM?

The Document Object Model is a tree-like representation of HTML that JavaScript can manipulate. Each HTML element becomes a node in the tree. The browser builds this from the parsed HTML.