Kilotest: Diagnoses of element unknown violation by HTML element 256 on Mozilla Foundation page

Basics

About the Mozilla Foundation page

• URL: https://www.mozilla.org/en-US/
• Tested 30 days ago by job 9wj on 2026-05-03 at 04:32

About HTML element 256

• Tag name: BLINK
• Text: Products … About us
• Start tag: <blink class="spacer-gif">
• XPath: /html/body/nav[1]/div[1]/div[1]/blink[1]
• Bounding box: x = 1548, y = 16, width = 100, height = 0

About the element unknown issue

• Why it matters: Document includes an unknown element that the browser cannot process
• Priority: highest
• Related WCAG standard: 4.1

Diagnoses

Here is how tools diagnose the element unknown issue for HTML element 256 of the Mozilla Foundation page.

1. The blink element is a completely-unknown element that is not allowed anywhere in any HTML content.

   Tool: Html Checker API (World Wide Web Consortium)