Code Fix Guide

How to Fix Common HTML Errors

Invalid HTML — unclosed tags, duplicate IDs, deprecated elements, and improper nesting — causes unpredictable rendering across browsers and breaks assistive technology. While modern browsers are forgiving of HTML errors, screen readers and other assistive tools are not.

Common Errors and How to Fix Them

Duplicate ID attributes — breaks label associations and ARIA

Problem

<div id="main">...</div>
<div id="main">...</div>

Fix

<div id="main-content">...</div>
<div id="sidebar">...</div>

Block element inside inline element — invalid nesting

Problem

<p>Paragraph with <div>a div inside</div> it</p>

Fix

<p>Paragraph text</p>
<div>Block content</div>
<p>More paragraph text</p>

Non-li children inside ul — invalid

Problem

<ul>
  <div>Item 1</div>
  <div>Item 2</div>
</ul>

Fix

<ul>
  <li>Item 1</li>
  <li>Item 2</li>
</ul>

Nested anchor tags — invalid and confusing

Problem

<a href="/page1">
  <a href="/page2">Nested link</a>
</a>

Fix

<a href="/page1">Page 1</a>
<a href="/page2">Page 2</a>

Why This Matters

Invalid HTML can violate multiple WCAG criteria depending on the specific error. Duplicate IDs break label associations (3.3.2), improper nesting breaks semantic structure (1.3.1), and missing closing tags can cause entire sections to be hidden from assistive technology. Use the W3C HTML Validator alongside ADA CodeFix for complete coverage.

Related WCAG Criteria

1.3.1Info and Relationships

Level A — Perceivable

4.1.2Name, Role, Value

Level A — Robust

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