Attribute “<” not allowed on element “X” at this point.

When the HTML parser encounters a < character inside an opening tag, it doesn’t treat it as the start of a new tag — instead, it tries to interpret it as an attribute name. Since < is not a valid attribute name, the W3C validator raises this error. The browser may still render the page, but the behavior is undefined and can vary across different browsers, potentially leading to broken markup or elements that don’t display correctly.

This issue most commonly occurs in a few scenarios:

• Accidental keystrokes — a stray < typed while editing attributes.
• Copy-paste artifacts — fragments of other tags getting pasted into the middle of an element.
• Misplaced angle brackets — attempting to nest or close tags incorrectly, such as adding < before /> in a self-closing tag.
• Template or code generation errors — dynamic HTML output that incorrectly injects < into attribute positions.

Because this is a syntax-level problem, it can cause cascading parse errors. The parser may misinterpret everything after the stray < until it finds a matching >, which can swallow subsequent elements or attributes and produce unexpected rendering results.

How to Fix It

1. Open the file referenced by the validator error and go to the indicated line number.
2. Look inside the opening tag of the flagged element for a < character that doesn’t belong.
3. Remove the stray < character.
4. If the < was meant to represent a literal less-than sign in an attribute value, replace it with the HTML entity <.

Examples

Stray < before the closing slash

<!-- ❌ Stray "<" before the self-closing slash -->

<img src="photo.jpg" alt="smiling cat" < />

<!-- ✅ Fixed: removed the stray "<" -->

<img src="photo.jpg" alt="smiling cat" />

Stray < between attributes

<!-- ❌ Accidental "<" between attributes -->

<a href="/about" < class="nav-link">About</a>

<!-- ✅ Fixed: removed the stray "<" -->

<a href="/about" class="nav-link">About</a>

Fragment of another tag pasted inside an element

<!-- ❌ Leftover "<span" pasted inside the div's opening tag -->

<div class="card" <span>
  <p>Hello world</p>
</div>

<!-- ✅ Fixed: removed the pasted fragment -->

<div class="card">
  <p>Hello world</p>
</div>

Literal < intended in an attribute value

If you actually need a less-than sign inside an attribute value — for example, in a title or data-* attribute — use the < entity instead of a raw <.

<!-- ❌ Raw "<" in an attribute value can cause parsing issues -->

<span title="x < 10">Threshold</span>

<!-- ✅ Fixed: use the HTML entity -->

<span title="x &lt; 10">Threshold</span>

Learn more:

MDN Reference

HTML attribute reference

→

WHATWG Spec

HTML syntax

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