Kilotest: Violations of attribute value invalid issue for Mozilla Foundation page

Basics

About the page

• URL: https://www.mozilla.org/en-US/
• Tested 32 days ago on 2026-09-08 at 04:02 by job 260908T0359-xmh
• Summary of results:
  • Rule engines:
    • Called: 12
    • Were able to test: 12
    • Reported any rule violations: 11
  • Violations: 753
  • Violators: 192
  • Issues: 47
• Download the full technical report (JSON)

About the issue

• Why it matters: Item behaves improperly
• Priority: highest
• Related WCAG standard: 1.3.1
• Reported by 1 rule engine (Html Checker API)
• Violations: 6
• Violators: 6

Violators

Here are the HTML elements reported to violate rules belonging to the attribute value invalid issue.

• Element 400

  • Tag name: IMG
  • Text: [not applicable]
  • Start tag: <img src="https://www.mozilla.org/media/cms/images/collective-mobile-1450.2e16d0ba.fill-400x400.jpg" srcset="https://www.mozilla.org/media/cms/images/collective-mobile-1450.2e16d0ba.fill-400x400.jpg 400w, https://www.mozilla.org/media/cms/images/collective-mobile-1450.2e16d0ba.fill-600x600.jpg 600w, https://www.mozilla.org/media/cms/images/collective-mobile-1450.2e16d0ba.fill-800x800.jpg 724w, https://www.mozilla.org/media/cms/images/collective-mobile-1450.2e16d0ba.fill-1000x1000.jpg 724w, https://www.mozilla.org/media/cms/images/collective-mobile-1450.2e16d0ba.fill-1200x1200.jpg 724w, https://www.mozilla.org/media/cms/images/collective-mobile-1450.2e16d0ba.fill-1400x1400.jpg 724w" sizes="(min-width: 1440px) 448px, calc((100vw - 64px) / 3)" width="1400" height="1400" loading="lazy" alt="">
  • XPath: /html/body/div[2]/main[1]/section[1]/div[1]/div[1]/div[1]/div[1]/picture[1]/img[1]
  • Bounding box: x = 272, y = 2726, width = 448, height = 448
  • Reported by Html Checker API
  • What diagnoses were reported?

• Element 413

  • Tag name: IMG
  • Text: [not applicable]
  • Start tag: <img src="https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-400x400.jpg" srcset="https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-400x400.jpg 400w, https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-600x600.jpg 600w, https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-800x800.jpg 800w, https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-1000x1000.jpg 1000w, https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-1200x1200.jpg 1200w, https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-1400x1400.jpg 1200w" sizes="(min-width: 1440px) 448px, calc((100vw - 64px) / 3)" width="1400" height="1400" loading="lazy" alt="">
  • XPath: /html/body/div[2]/main[1]/section[1]/div[1]/div[1]/div[2]/div[1]/picture[1]/img[1]
  • Bounding box: x = 736, y = 2726, width = 448, height = 448
  • Reported by Html Checker API
  • What diagnoses were reported?

• Element 412

  • Tag name: SOURCE
  • Text: [not applicable]
  • Start tag: <source media="(max-width: 1311px)" srcset="https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-400x200.jpg 400w, https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-600x300.jpg 600w, https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-800x400.jpg 800w, https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-1000x500.jpg 1000w, https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-1200x600.jpg 1200w, https://www.mozilla.org/media/cms/images/image1.2e16d0ba.fill-1400x700.jpg 1200w" sizes="(min-width: 768px) calc((100vw - 32px) / 2), calc(100vw - 32px)" width="1400" height="700">
  • XPath: /html/body/div[2]/main[1]/section[1]/div[1]/div[1]/div[2]/div[1]/picture[1]/source[1]
  • Bounding box: x = 736, y = 2726, width = 0, height = 0
  • Reported by Html Checker API
  • What diagnoses were reported?

• Element 426

  • Tag name: IMG
  • Text: [not applicable]
  • Start tag: <img src="https://www.mozilla.org/media/cms/images/lamp-mobile-1450.2e16d0ba.fill-400x400.jpg" srcset="https://www.mozilla.org/media/cms/images/lamp-mobile-1450.2e16d0ba.fill-400x400.jpg 400w, https://www.mozilla.org/media/cms/images/lamp-mobile-1450.2e16d0ba.fill-600x600.jpg 600w, https://www.mozilla.org/media/cms/images/lamp-mobile-1450.2e16d0ba.fill-800x800.jpg 724w, https://www.mozilla.org/media/cms/images/lamp-mobile-1450.2e16d0ba.fill-1000x1000.jpg 724w, https://www.mozilla.org/media/cms/images/lamp-mobile-1450.2e16d0ba.fill-1200x1200.jpg 724w, https://www.mozilla.org/media/cms/images/lamp-mobile-1450.2e16d0ba.fill-1400x1400.jpg 724w" sizes="(min-width: 1440px) 448px, calc((100vw - 64px) / 3)" width="1400" height="1400" loading="lazy" alt="Image of Mark Surman">
  • XPath: /html/body/div[2]/main[1]/section[1]/div[1]/div[1]/div[3]/div[1]/picture[1]/img[1]
  • Bounding box: x = 1200, y = 2726, width = 448, height = 448
  • Reported by Html Checker API
  • What diagnoses were reported?

• Element 439

  • Tag name: IMG
  • Text: [not applicable]
  • Start tag: <img src="https://www.mozilla.org/media/cms/images/ventures-mobile-1450_PAi6k2A.2e16d0ba.fill-400x400.jpg" srcset="https://www.mozilla.org/media/cms/images/ventures-mobile-1450_PAi6k2A.2e16d0ba.fill-400x400.jpg 400w, https://www.mozilla.org/media/cms/images/ventures-mobile-1450_GxBP35h.2e16d0ba.fill-600x600.jpg 600w, https://www.mozilla.org/media/cms/images/ventures-mobile-1450_LGUvtES.2e16d0ba.fill-800x800.jpg 728w, https://www.mozilla.org/media/cms/images/ventures-mobile-1450_7KZofzQ.2e16d0ba.fill-1000x1000.jpg 728w, https://www.mozilla.org/media/cms/images/ventures-mobile-1450_zdwzhgf.2e16d0ba.fill-1200x1200.jpg 728w, https://www.mozilla.org/media/cms/images/ventures-mobile-1450_FJAYBDE.2e16d0ba.fill-1400x1400.jpg 728w" sizes="(min-width: 1440px) 448px, calc((100vw - 64px) / 3)" width="1400" height="1400" loading="lazy" alt="">
  • XPath: /html/body/div[2]/main[1]/section[1]/div[1]/div[1]/div[4]/div[1]/picture[1]/img[1]
  • Bounding box: x = 272, y = 3372, width = 448, height = 448
  • Reported by Html Checker API
  • What diagnoses were reported?

• Element 452

  • Tag name: IMG
  • Text: [not applicable]
  • Start tag: <img src="https://www.mozilla.org/media/cms/images/ecosystem-mobile-1450.2e16d0ba.fill-400x400.jpg" srcset="https://www.mozilla.org/media/cms/images/ecosystem-mobile-1450.2e16d0ba.fill-400x400.jpg 400w, https://www.mozilla.org/media/cms/images/ecosystem-mobile-1450.2e16d0ba.fill-600x600.jpg 600w, https://www.mozilla.org/media/cms/images/ecosystem-mobile-1450.2e16d0ba.fill-800x800.jpg 724w, https://www.mozilla.org/media/cms/images/ecosystem-mobile-1450.2e16d0ba.fill-1000x1000.jpg 724w, https://www.mozilla.org/media/cms/images/ecosystem-mobile-1450.2e16d0ba.fill-1200x1200.jpg 724w, https://www.mozilla.org/media/cms/images/ecosystem-mobile-1450.2e16d0ba.fill-1400x1400.jpg 724w" sizes="(min-width: 1440px) 448px, calc((100vw - 64px) / 3)" width="1400" height="1400" loading="lazy" alt="">
  • XPath: /html/body/div[2]/main[1]/section[1]/div[1]/div[1]/div[5]/div[1]/picture[1]/img[1]
  • Bounding box: x = 736, y = 3372, width = 448, height = 448
  • Reported by Html Checker API
  • What diagnoses were reported?