📘 DAY 10: HTML COMMENTS 

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1️⃣ What are HTML Comments?

HTML comments are used to:

• Add notes inside HTML code

• Explain code for developers

• Temporarily disable code

👉 Comments are not displayed in the browser.

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2️⃣ HTML Comment Syntax

HTML comments are written using:

<!-- This is a comment -->

Anything inside <!-- --> is ignored by the browser.

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3️⃣ Simple Example

<!-- This is a heading -->
<h1>Welcome</h1>

<!-- This is a paragraph -->
<p>Hello HTML</p>

Output in browser:

Welcome
Hello HTML

👉 Comments are invisible to users.

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4️⃣ Multi-line Comments

HTML supports multi-line comments.

<!--
This is a multi-line comment.
Used to explain large code blocks.
-->

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5️⃣ Commenting Out HTML Code

Comments are often used to disable code temporarily.

<!-- <p>This paragraph is hidden</p> -->

👉 The paragraph will not appear in the browser.

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6️⃣ Why Use HTML Comments?

HTML comments are useful for:
✔ Understanding code
✔ Debugging
✔ Team collaboration
✔ Organizing large HTML files

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7️⃣ Comments for Section Marking

<!-- Header Section -->
<header>
  <h1>My Website</h1>
</header>

<!-- Main Content -->
<main>
  <p>Content here</p>
</main>

👉 Makes code clean & readable

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8️⃣ HTML Comments and Security

⚠️ Comments are visible in page source
(Right click → View Page Source)

❌ Do NOT write:

• Passwords

• API keys

• Confidential information

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9️⃣ Invalid HTML Comment (Wrong)

❌ This will cause issues:

<!---- This is wrong --->

❌ Nested comments:

<!-- Comment <!-- nested --> -->

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🔟 Correct HTML Comment Rules

✔ Start with <!--
✔ End with -->
✔ No nested comments
✔ No sensitive data

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1️⃣1️⃣ Common Beginner Mistakes

❌ Forgetting closing -->
❌ Writing comments inside tags
❌ Expecting comments to show output
❌ Using comments for styling

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1️⃣2️⃣ Comments vs Text

Comment	Text
Not visible	Visible
For developers	For users
Ignored by browser	Rendered

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1️⃣3️⃣ Practice Example

<!-- Page Title -->
<h1>HTML Comments</h1>

<!-- Description -->
<p>This page explains comments.</p>

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1️⃣4️⃣ Interview / Viva Questions

1. What are HTML comments?

2. What is the syntax of HTML comments?

3. Are comments visible to users?

4. Can we write multi-line comments?

5. Why should we avoid sensitive data in comments?

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1️⃣5️⃣ Summary

• HTML comments explain code

• Not displayed in browser

• Used for debugging & readability

• Follow proper syntax

• Avoid sensitive data