HTML Checking for Large Sites
Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.
A <button>
tag can’t include other <button>
tags inside. Most probable cause is an unclosed <button>
tag, like in this example:
<button>Submit
<button>Cancel</button>
Related W3C validator issues
An <a> tag can’t include other <a> tags inside. Most probable cause is an unclosed <a> tag, like in this example:
<a href="one.html">Page 1
<a href="two.html">Page 2</a>
A button element, or an element with the role=button attribute, is not allowed to be nested inside an <a> element.
A button element cannot contain a descendant element with the attribute tabindex.
The aria-expanded attribute can only be true, false, or undefined.
This attribute indicates whether a grouping element is expanded or collapsed.
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An element like <h1>, <h2>, etc., used to define a heading, does not accept the button role.
The following HTML code is invalid because the <h2> element can’t have role="button"
<h2 role="button">Some heading</h2>
Instead, you can nest the <h2> inside a <div> with that role. In this case however, browsers automatically apply role presentation to all descendant elements of any button element as it is a role that does not support semantic children.
<div role="button">
<h2>Some heading</h2>
</div>
A <li> element, used to define a list item, does not accept the button role.
This HTML code is invalid because the <li> elements can’t have role="button":
<ul>
<li role="button">One</li>
<li role="button">Two</li>
</ul>
6,250 HTML checks per week. Fully automated.
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A <div> tag has been found as a direct child of an <ul> tag, and this is not allowed. For example, <ul><div><li>item</li></div></ul> is not valid, but <ul><li><div>item</div></li></ul> is valid as the direct child of <ul> is <li>.
The element X is not allowed as a child element of Y. For example, a <ul> element cannot have a <div> child element.
An </a> end tag has been found to violate nesting rules. <a> tags can’t include other <a> tags inside. Most probable cause is an unclosed <a> tag, like in this example:
<a href="one.html">Page 1
<a href="two.html">Page 2</a>
An end tag </code> has been found violating nesting rules. Check other errors in the same document related to the <code> element, and fix the unallowed nested elements.
25,000 HTML checks per month. Fully automated.
Save time using our automated web checker. Let our crawler check your web pages on the W3C Validator.