HTML • Chapter 15 • Foundations to Production
Responsive Images
Each topic contains substantial explanation, ten focused teaching examples, its own HTML code example, code reasoning, expected browser result, and practice.
15.1 srcset
srcset is part of the HTML structure covered in Chapter 15. HTML communicates meaning and document relationships to browsers, search engines, assistive technology, and other tools, so the choice of element or attribute should match the content rather than only its visual appearance.
For srcset, examine the element's permitted content, relevant attributes, semantic meaning, accessibility effect, and how it behaves when CSS or JavaScript is unavailable. In responsive images, the markup should remain understandable as a document before presentation is added.
In Chapter 15, a reliable way to learn srcset is to write a small valid fragment, inspect the browser result and document outline, then test one incorrect or missing attribute. This makes the reason for each piece of markup visible instead of treating HTML as a collection of tags to memorize.
Concept in plain language
srcset is part of the HTML structure covered in Chapter 15. HTML communicates meaning and document relationships to browsers, search engines, assistive technology, and other tools, so the choice of element or attribute should match the content rather than only its visual appearance.
10 teaching examples
Example 1: Minimal markup
Create the smallest valid contact page example that demonstrates srcset. Identify which part carries meaning and which parts are only supporting structure. This is Chapter 15, topic 1, example 1.
Example 2: Content variation
Change the text or resource used by srcset in the product description. Confirm that the markup still describes the new content correctly instead of depending on the old wording. This is Chapter 15, topic 1, example 2.
Example 3: Missing-information test
Remove one important attribute or related element from the profile page example using srcset. Explain what meaning, accessibility, navigation, or browser behavior is lost. This is Chapter 15, topic 1, example 3.
Example 4: Accessibility review
Read the documentation page example using the semantics of srcset. Check names, labels, landmarks, alternatives, focus behavior, and whether the content still makes sense without styling. This is Chapter 15, topic 1, example 4.
Example 5: Mobile review
Open the event page markup containing srcset on a narrow screen. Ensure embedded content, long text, controls, and translated labels do not force the page wider than the viewport. This is Chapter 15, topic 1, example 5.
Example 6: RTL review
Translate the FAQ page into Arabic or Persian. Keep document text RTL where appropriate while URLs, code samples, numbers, and intentionally LTR fragments remain readable. This is Chapter 15, topic 1, example 6.
Example 7: Validation exercise
Run the photo story fragment using srcset through an HTML validator. Fix invalid nesting, duplicate IDs, missing required attributes, or obsolete markup before adding extra features. This is Chapter 15, topic 1, example 7.
Example 8: Progressive-enhancement check
Use srcset in the support page so the core content remains useful before CSS and JavaScript load. Add enhancement only after the document structure is complete. This is Chapter 15, topic 1, example 8.
Example 9: SEO and semantics review
Inspect how srcset contributes to the meaning of the dashboard shell. Keep headings, links, metadata, and document regions consistent so crawlers and users receive the same primary content. This is Chapter 15, topic 1, example 9.
Example 10: Production review
Review srcset in the language page for validity, accessibility, security-related attributes, performance hints, responsive behavior, localization, and maintainability. This is Chapter 15, topic 1, example 10.
HTML code example
<picture>
<source media="(max-width: 600px)" srcset="/images/lesson-mobile.webp">
<img src="/images/lesson-wide.webp" srcset="/images/lesson-800.webp 800w, /images/lesson-1400.webp 1400w" sizes="(max-width: 900px) 100vw, 900px" alt="Students working through an HTML lesson" width="1400" height="788">
</picture>Step-by-step code explanation
- Identify the element or attribute responsible for srcset.
- Read the markup from the outer document structure inward and verify that each child is allowed in its parent context.
- Check the semantic meaning and any accessibility relationship such as labels, alternatives, headings, captions, or landmarks.
- Open the fragment in a browser and compare the rendered result with the source instead of assuming visual appearance proves validity.
- Validate the markup and test responsive, RTL, and no-JavaScript behavior where they apply.
Expected browser result: The browser displays or exposes the structure appropriate for srcset while preserving the semantic relationships expressed by the markup.
Practice exercise
Write a fresh HTML fragment for srcset in Chapter 15. Validate it, remove one important attribute or related element to observe the difference, then restore the correct markup. Test the result with keyboard navigation when interactive, on a narrow screen, and in Arabic or Persian when the content can be translated.
15.2 sizes
sizes is part of the HTML structure covered in Chapter 15. HTML communicates meaning and document relationships to browsers, search engines, assistive technology, and other tools, so the choice of element or attribute should match the content rather than only its visual appearance.
For sizes, examine the element's permitted content, relevant attributes, semantic meaning, accessibility effect, and how it behaves when CSS or JavaScript is unavailable. In responsive images, the markup should remain understandable as a document before presentation is added.
In Chapter 15, a reliable way to learn sizes is to write a small valid fragment, inspect the browser result and document outline, then test one incorrect or missing attribute. This makes the reason for each piece of markup visible instead of treating HTML as a collection of tags to memorize.
Concept in plain language
sizes is part of the HTML structure covered in Chapter 15. HTML communicates meaning and document relationships to browsers, search engines, assistive technology, and other tools, so the choice of element or attribute should match the content rather than only its visual appearance.
10 teaching examples
Example 1: Minimal markup
Create the smallest valid profile page example that demonstrates sizes. Identify which part carries meaning and which parts are only supporting structure. This is Chapter 15, topic 2, example 1.
Example 2: Content variation
Change the text or resource used by sizes in the documentation page. Confirm that the markup still describes the new content correctly instead of depending on the old wording. This is Chapter 15, topic 2, example 2.
Example 3: Missing-information test
Remove one important attribute or related element from the event page example using sizes. Explain what meaning, accessibility, navigation, or browser behavior is lost. This is Chapter 15, topic 2, example 3.
Example 4: Accessibility review
Read the FAQ page example using the semantics of sizes. Check names, labels, landmarks, alternatives, focus behavior, and whether the content still makes sense without styling. This is Chapter 15, topic 2, example 4.
Example 5: Mobile review
Open the photo story markup containing sizes on a narrow screen. Ensure embedded content, long text, controls, and translated labels do not force the page wider than the viewport. This is Chapter 15, topic 2, example 5.
Example 6: RTL review
Translate the support page into Arabic or Persian. Keep document text RTL where appropriate while URLs, code samples, numbers, and intentionally LTR fragments remain readable. This is Chapter 15, topic 2, example 6.
Example 7: Validation exercise
Run the dashboard shell fragment using sizes through an HTML validator. Fix invalid nesting, duplicate IDs, missing required attributes, or obsolete markup before adding extra features. This is Chapter 15, topic 2, example 7.
Example 8: Progressive-enhancement check
Use sizes in the language page so the core content remains useful before CSS and JavaScript load. Add enhancement only after the document structure is complete. This is Chapter 15, topic 2, example 8.
Example 9: SEO and semantics review
Inspect how sizes contributes to the meaning of the booking page. Keep headings, links, metadata, and document regions consistent so crawlers and users receive the same primary content. This is Chapter 15, topic 2, example 9.
Example 10: Production review
Review sizes in the media page for validity, accessibility, security-related attributes, performance hints, responsive behavior, localization, and maintainability. This is Chapter 15, topic 2, example 10.
HTML code example
<picture>
<source media="(max-width: 600px)" srcset="/images/lesson-mobile.webp">
<img src="/images/lesson-wide.webp" srcset="/images/lesson-800.webp 800w, /images/lesson-1400.webp 1400w" sizes="(max-width: 900px) 100vw, 900px" alt="Students working through an HTML lesson" width="1400" height="788">
</picture>Step-by-step code explanation
- Identify the element or attribute responsible for sizes.
- Read the markup from the outer document structure inward and verify that each child is allowed in its parent context.
- Check the semantic meaning and any accessibility relationship such as labels, alternatives, headings, captions, or landmarks.
- Open the fragment in a browser and compare the rendered result with the source instead of assuming visual appearance proves validity.
- Validate the markup and test responsive, RTL, and no-JavaScript behavior where they apply.
Expected browser result: The browser displays or exposes the structure appropriate for sizes while preserving the semantic relationships expressed by the markup.
Practice exercise
Write a fresh HTML fragment for sizes in Chapter 15. Validate it, remove one important attribute or related element to observe the difference, then restore the correct markup. Test the result with keyboard navigation when interactive, on a narrow screen, and in Arabic or Persian when the content can be translated.
15.3 picture Element
picture Element is part of the HTML structure covered in Chapter 15. HTML communicates meaning and document relationships to browsers, search engines, assistive technology, and other tools, so the choice of element or attribute should match the content rather than only its visual appearance.
For picture Element, examine the element's permitted content, relevant attributes, semantic meaning, accessibility effect, and how it behaves when CSS or JavaScript is unavailable. In responsive images, the markup should remain understandable as a document before presentation is added.
In Chapter 15, a reliable way to learn picture Element is to write a small valid fragment, inspect the browser result and document outline, then test one incorrect or missing attribute. This makes the reason for each piece of markup visible instead of treating HTML as a collection of tags to memorize.
Concept in plain language
picture Element is part of the HTML structure covered in Chapter 15. HTML communicates meaning and document relationships to browsers, search engines, assistive technology, and other tools, so the choice of element or attribute should match the content rather than only its visual appearance.
10 teaching examples
Example 1: Minimal markup
Create the smallest valid event page example that demonstrates picture Element. Identify which part carries meaning and which parts are only supporting structure. This is Chapter 15, topic 3, example 1.
Example 2: Content variation
Change the text or resource used by picture Element in the FAQ page. Confirm that the markup still describes the new content correctly instead of depending on the old wording. This is Chapter 15, topic 3, example 2.
Example 3: Missing-information test
Remove one important attribute or related element from the photo story example using picture Element. Explain what meaning, accessibility, navigation, or browser behavior is lost. This is Chapter 15, topic 3, example 3.
Example 4: Accessibility review
Read the support page example using the semantics of picture Element. Check names, labels, landmarks, alternatives, focus behavior, and whether the content still makes sense without styling. This is Chapter 15, topic 3, example 4.
Example 5: Mobile review
Open the dashboard shell markup containing picture Element on a narrow screen. Ensure embedded content, long text, controls, and translated labels do not force the page wider than the viewport. This is Chapter 15, topic 3, example 5.
Example 6: RTL review
Translate the language page into Arabic or Persian. Keep document text RTL where appropriate while URLs, code samples, numbers, and intentionally LTR fragments remain readable. This is Chapter 15, topic 3, example 6.
Example 7: Validation exercise
Run the booking page fragment using picture Element through an HTML validator. Fix invalid nesting, duplicate IDs, missing required attributes, or obsolete markup before adding extra features. This is Chapter 15, topic 3, example 7.
Example 8: Progressive-enhancement check
Use picture Element in the media page so the core content remains useful before CSS and JavaScript load. Add enhancement only after the document structure is complete. This is Chapter 15, topic 3, example 8.
Example 9: SEO and semantics review
Inspect how picture Element contributes to the meaning of the school page. Keep headings, links, metadata, and document regions consistent so crawlers and users receive the same primary content. This is Chapter 15, topic 3, example 9.
Example 10: Production review
Review picture Element in the course lesson for validity, accessibility, security-related attributes, performance hints, responsive behavior, localization, and maintainability. This is Chapter 15, topic 3, example 10.
HTML code example
<picture>
<source media="(max-width: 600px)" srcset="/images/lesson-mobile.webp">
<img src="/images/lesson-wide.webp" srcset="/images/lesson-800.webp 800w, /images/lesson-1400.webp 1400w" sizes="(max-width: 900px) 100vw, 900px" alt="Students working through an HTML lesson" width="1400" height="788">
</picture>Step-by-step code explanation
- Identify the element or attribute responsible for picture Element.
- Read the markup from the outer document structure inward and verify that each child is allowed in its parent context.
- Check the semantic meaning and any accessibility relationship such as labels, alternatives, headings, captions, or landmarks.
- Open the fragment in a browser and compare the rendered result with the source instead of assuming visual appearance proves validity.
- Validate the markup and test responsive, RTL, and no-JavaScript behavior where they apply.
Expected browser result: The browser displays or exposes the structure appropriate for picture Element while preserving the semantic relationships expressed by the markup.
Practice exercise
Write a fresh HTML fragment for picture Element in Chapter 15. Validate it, remove one important attribute or related element to observe the difference, then restore the correct markup. Test the result with keyboard navigation when interactive, on a narrow screen, and in Arabic or Persian when the content can be translated.
15.4 source Element
source Element is part of the HTML structure covered in Chapter 15. HTML communicates meaning and document relationships to browsers, search engines, assistive technology, and other tools, so the choice of element or attribute should match the content rather than only its visual appearance.
For source Element, examine the element's permitted content, relevant attributes, semantic meaning, accessibility effect, and how it behaves when CSS or JavaScript is unavailable. In responsive images, the markup should remain understandable as a document before presentation is added.
In Chapter 15, a reliable way to learn source Element is to write a small valid fragment, inspect the browser result and document outline, then test one incorrect or missing attribute. This makes the reason for each piece of markup visible instead of treating HTML as a collection of tags to memorize.
Concept in plain language
source Element is part of the HTML structure covered in Chapter 15. HTML communicates meaning and document relationships to browsers, search engines, assistive technology, and other tools, so the choice of element or attribute should match the content rather than only its visual appearance.
10 teaching examples
Example 1: Minimal markup
Create the smallest valid photo story example that demonstrates source Element. Identify which part carries meaning and which parts are only supporting structure. This is Chapter 15, topic 4, example 1.
Example 2: Content variation
Change the text or resource used by source Element in the support page. Confirm that the markup still describes the new content correctly instead of depending on the old wording. This is Chapter 15, topic 4, example 2.
Example 3: Missing-information test
Remove one important attribute or related element from the dashboard shell example using source Element. Explain what meaning, accessibility, navigation, or browser behavior is lost. This is Chapter 15, topic 4, example 3.
Example 4: Accessibility review
Read the language page example using the semantics of source Element. Check names, labels, landmarks, alternatives, focus behavior, and whether the content still makes sense without styling. This is Chapter 15, topic 4, example 4.
Example 5: Mobile review
Open the booking page markup containing source Element on a narrow screen. Ensure embedded content, long text, controls, and translated labels do not force the page wider than the viewport. This is Chapter 15, topic 4, example 5.
Example 6: RTL review
Translate the media page into Arabic or Persian. Keep document text RTL where appropriate while URLs, code samples, numbers, and intentionally LTR fragments remain readable. This is Chapter 15, topic 4, example 6.
Example 7: Validation exercise
Run the school page fragment using source Element through an HTML validator. Fix invalid nesting, duplicate IDs, missing required attributes, or obsolete markup before adding extra features. This is Chapter 15, topic 4, example 7.
Example 8: Progressive-enhancement check
Use source Element in the course lesson so the core content remains useful before CSS and JavaScript load. Add enhancement only after the document structure is complete. This is Chapter 15, topic 4, example 8.
Example 9: SEO and semantics review
Inspect how source Element contributes to the meaning of the news article. Keep headings, links, metadata, and document regions consistent so crawlers and users receive the same primary content. This is Chapter 15, topic 4, example 9.
Example 10: Production review
Review source Element in the contact page for validity, accessibility, security-related attributes, performance hints, responsive behavior, localization, and maintainability. This is Chapter 15, topic 4, example 10.
HTML code example
<picture>
<source media="(max-width: 600px)" srcset="/images/lesson-mobile.webp">
<img src="/images/lesson-wide.webp" srcset="/images/lesson-800.webp 800w, /images/lesson-1400.webp 1400w" sizes="(max-width: 900px) 100vw, 900px" alt="Students working through an HTML lesson" width="1400" height="788">
</picture>Step-by-step code explanation
- Identify the element or attribute responsible for source Element.
- Read the markup from the outer document structure inward and verify that each child is allowed in its parent context.
- Check the semantic meaning and any accessibility relationship such as labels, alternatives, headings, captions, or landmarks.
- Open the fragment in a browser and compare the rendered result with the source instead of assuming visual appearance proves validity.
- Validate the markup and test responsive, RTL, and no-JavaScript behavior where they apply.
Expected browser result: The browser displays or exposes the structure appropriate for source Element while preserving the semantic relationships expressed by the markup.
Practice exercise
Write a fresh HTML fragment for source Element in Chapter 15. Validate it, remove one important attribute or related element to observe the difference, then restore the correct markup. Test the result with keyboard navigation when interactive, on a narrow screen, and in Arabic or Persian when the content can be translated.
15.5 Art Direction
Art Direction is part of the HTML structure covered in Chapter 15. HTML communicates meaning and document relationships to browsers, search engines, assistive technology, and other tools, so the choice of element or attribute should match the content rather than only its visual appearance.
For Art Direction, examine the element's permitted content, relevant attributes, semantic meaning, accessibility effect, and how it behaves when CSS or JavaScript is unavailable. In responsive images, the markup should remain understandable as a document before presentation is added.
In Chapter 15, a reliable way to learn Art Direction is to write a small valid fragment, inspect the browser result and document outline, then test one incorrect or missing attribute. This makes the reason for each piece of markup visible instead of treating HTML as a collection of tags to memorize.
Concept in plain language
Art Direction is part of the HTML structure covered in Chapter 15. HTML communicates meaning and document relationships to browsers, search engines, assistive technology, and other tools, so the choice of element or attribute should match the content rather than only its visual appearance.
10 teaching examples
Example 1: Minimal markup
Create the smallest valid dashboard shell example that demonstrates Art Direction. Identify which part carries meaning and which parts are only supporting structure. This is Chapter 15, topic 5, example 1.
Example 2: Content variation
Change the text or resource used by Art Direction in the language page. Confirm that the markup still describes the new content correctly instead of depending on the old wording. This is Chapter 15, topic 5, example 2.
Example 3: Missing-information test
Remove one important attribute or related element from the booking page example using Art Direction. Explain what meaning, accessibility, navigation, or browser behavior is lost. This is Chapter 15, topic 5, example 3.
Example 4: Accessibility review
Read the media page example using the semantics of Art Direction. Check names, labels, landmarks, alternatives, focus behavior, and whether the content still makes sense without styling. This is Chapter 15, topic 5, example 4.
Example 5: Mobile review
Open the school page markup containing Art Direction on a narrow screen. Ensure embedded content, long text, controls, and translated labels do not force the page wider than the viewport. This is Chapter 15, topic 5, example 5.
Example 6: RTL review
Translate the course lesson into Arabic or Persian. Keep document text RTL where appropriate while URLs, code samples, numbers, and intentionally LTR fragments remain readable. This is Chapter 15, topic 5, example 6.
Example 7: Validation exercise
Run the news article fragment using Art Direction through an HTML validator. Fix invalid nesting, duplicate IDs, missing required attributes, or obsolete markup before adding extra features. This is Chapter 15, topic 5, example 7.
Example 8: Progressive-enhancement check
Use Art Direction in the contact page so the core content remains useful before CSS and JavaScript load. Add enhancement only after the document structure is complete. This is Chapter 15, topic 5, example 8.
Example 9: SEO and semantics review
Inspect how Art Direction contributes to the meaning of the product description. Keep headings, links, metadata, and document regions consistent so crawlers and users receive the same primary content. This is Chapter 15, topic 5, example 9.
Example 10: Production review
Review Art Direction in the profile page for validity, accessibility, security-related attributes, performance hints, responsive behavior, localization, and maintainability. This is Chapter 15, topic 5, example 10.
HTML code example
<picture>
<source media="(max-width: 600px)" srcset="/images/lesson-mobile.webp">
<img src="/images/lesson-wide.webp" srcset="/images/lesson-800.webp 800w, /images/lesson-1400.webp 1400w" sizes="(max-width: 900px) 100vw, 900px" alt="Students working through an HTML lesson" width="1400" height="788">
</picture>Step-by-step code explanation
- Identify the element or attribute responsible for Art Direction.
- Read the markup from the outer document structure inward and verify that each child is allowed in its parent context.
- Check the semantic meaning and any accessibility relationship such as labels, alternatives, headings, captions, or landmarks.
- Open the fragment in a browser and compare the rendered result with the source instead of assuming visual appearance proves validity.
- Validate the markup and test responsive, RTL, and no-JavaScript behavior where they apply.
Expected browser result: The browser displays or exposes the structure appropriate for Art Direction while preserving the semantic relationships expressed by the markup.
Practice exercise
Write a fresh HTML fragment for Art Direction in Chapter 15. Validate it, remove one important attribute or related element to observe the difference, then restore the correct markup. Test the result with keyboard navigation when interactive, on a narrow screen, and in Arabic or Persian when the content can be translated.
Chapter 15 review — 10 questions and answers
1. What should you check first when using srcset?
Answer: Check that the markup for srcset matches the meaning of the content, is valid in its context, and does not depend on visual styling to communicate essential information.
2. How do you review srcset before publishing?
Answer: Validate the HTML, inspect accessibility and keyboard behavior where relevant, test narrow screens and translated text, and confirm that srcset adds real document meaning or browser behavior.
3. What should you check first when using sizes?
Answer: Check that the markup for sizes matches the meaning of the content, is valid in its context, and does not depend on visual styling to communicate essential information.
4. How do you review sizes before publishing?
Answer: Validate the HTML, inspect accessibility and keyboard behavior where relevant, test narrow screens and translated text, and confirm that sizes adds real document meaning or browser behavior.
5. What should you check first when using picture Element?
Answer: Check that the markup for picture Element matches the meaning of the content, is valid in its context, and does not depend on visual styling to communicate essential information.
6. How do you review picture Element before publishing?
Answer: Validate the HTML, inspect accessibility and keyboard behavior where relevant, test narrow screens and translated text, and confirm that picture Element adds real document meaning or browser behavior.
7. What should you check first when using source Element?
Answer: Check that the markup for source Element matches the meaning of the content, is valid in its context, and does not depend on visual styling to communicate essential information.
8. How do you review source Element before publishing?
Answer: Validate the HTML, inspect accessibility and keyboard behavior where relevant, test narrow screens and translated text, and confirm that source Element adds real document meaning or browser behavior.
9. What should you check first when using Art Direction?
Answer: Check that the markup for Art Direction matches the meaning of the content, is valid in its context, and does not depend on visual styling to communicate essential information.
10. How do you review Art Direction before publishing?
Answer: Validate the HTML, inspect accessibility and keyboard behavior where relevant, test narrow screens and translated text, and confirm that Art Direction adds real document meaning or browser behavior.