Here are the Top 20 Advanced HTML Interview Questions and Answers for experienced web developers:

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1. What are data- attributes in HTML5?*

Answer:
data-* attributes allow you to store extra information (custom data) on HTML elements without using JavaScript or cluttering class/id attributes.

<div data-user-id="12345" data-role="admin">User Info</div>

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2. Explain the difference between <script defer> and <script async>.

Answer:

• async: Script is executed as soon as it’s downloaded. Doesn’t guarantee order.
• defer: Script is executed after HTML is parsed, in order.

<script src="script.js" async></script>
<script src="script.js" defer></script>

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3. What is the purpose of the rel="noopener noreferrer" attribute in anchor tags?

Answer:
Used to:

• Improve security by preventing access to window.opener.
• Avoid performance issues and phishing attacks.

<a href="https://example.com" target="_blank" rel="noopener noreferrer">Visit</a>

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4. What is the difference between <section> and <div>?

Answer:

• <section>: Semantic element used for thematic grouping with headings.
• <div>: Generic container, non-semantic.

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Top 20 Advanced HTML Interview Questions and Answers

5. What is the purpose of the <template> tag?

Answer:
Holds client-side content that is not rendered until it is activated via JavaScript.

<template id="my-template">
  <p>Hello, this is a template!</p>
</template>

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6. How is contenteditable used in HTML?

Answer:
Makes an element editable in the browser.

<div contenteditable="true">Edit me!</div>

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7. What’s the difference between localStorage, sessionStorage, and cookies in HTML5?

Answer:

• localStorage: Persistent, no expiry.
• sessionStorage: Clears on tab close.
• Cookies: Sent with every HTTP request, size-limited (~4KB).

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8. What are the main differences between HTML4 and HTML5?

Answer:

• New semantic tags (<article>, <section>, <header>)
• Multimedia support (<audio>, <video>)
• localStorage, canvas, geolocation API

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9. What is the use of the <meta charset="UTF-8"> tag?

Answer:
Defines character encoding, supports special characters like emojis and symbols.

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10. What is the role of ARIA (Accessible Rich Internet Applications) attributes?

Answer:
Used to improve accessibility for screen readers and assistive tech.
Example:

<div role="button" aria-pressed="false">Toggle</div>

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Top 20 Advanced HTML Interview Questions and Answers

11. What are semantic HTML elements and why are they important?

Answer:
They convey meaning and improve SEO and accessibility.
Examples: <article>, <footer>, <nav>, <aside>.

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12. How does the <picture> element differ from <img>?

Answer:
<picture> allows serving different images based on device conditions (e.g., screen size, resolution).

<picture>
  <source media="(min-width: 800px)" srcset="large.jpg">
  <img src="small.jpg" alt="Responsive Image">
</picture>

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13. What is the difference between id and class in HTML?

Answer:

• id: Unique, used once per page.
• class: Can be reused, allows grouping.

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14. What does the download attribute do in anchor tags?

Answer:
Forces the browser to download the file instead of navigating.

<a href="file.pdf" download>Download PDF</a>

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15. What is Shadow DOM and how is it related to HTML?

Answer:
It allows encapsulation of HTML, CSS, and JavaScript in web components.

const shadow = element.attachShadow({ mode: 'open' });
shadow.innerHTML = `<style>p { color: red; }</style><p>Hello</p>`;

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Top 20 Advanced HTML Interview Questions and Answers

16. How can you validate HTML5 forms without JavaScript?

Answer:
Using attributes like:

• required
• pattern
• minlength, maxlength
• type="email" etc.

<input type="email" required pattern=".+@example\.com">

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17. What is the difference between <b> and <strong>, <i> and <em>?

Answer:

• <strong> / <em>: Have semantic meaning (importance/emphasis).
• <b> / <i>: Purely stylistic.

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18. How can you embed SVG directly in HTML?

Answer:

<svg width="100" height="100">
  <circle cx="50" cy="50" r="40" stroke="black" fill="red" />
</svg>

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19. What is the sandbox attribute in iframes?

Answer:
Applies restrictions to content within an iframe.

<iframe src="page.html" sandbox="allow-scripts allow-forms"></iframe>

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20. What are void (self-closing) elements in HTML?

Answer:
Elements that don’t need closing tags:
Examples: <br>, <img>, <hr>, <meta>, <input>

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Top 20 Advanced HTML Interview Questions and Answers

Top 20 Advanced HTML Interview Questions and Answers

Top 20 Advanced HTML Interview Questions and Answers