HTML Guide
Empty name attributes on <a> are invalid; an anchor’s name/id must be a non-empty unique identifier.
Historically, the name attribute on <a> was used to create fragment targets (e.g., <a name="top"></a>). In HTML5/living standard, fragment navigation should use the id attribute instead. The name attribute on <a> is obsolete for this purpose, and an empty string is never allowed for identifiers.
Use id with a non-empty value to create link targets, and point to them with href="#idValue". If you keep name for legacy reasons, it must still be non-empty and match the HTML syntax for valid IDs. Avoid adding empty attributes like name="" or id="". Also ensure uniqueness of each id in the document.
HTML Examples
Example causing the validator error
<!doctype html>
<html lang="en">
<head>
<title>Anchor name error</title>
</head>
<body>
<a name=""></a>
<a href="#"></a>
</body>
</html>Corrected example using id (recommended)
<!doctype html>
<html lang="en">
<head>
<title>Anchor id fix</title>
</head>
<body>
<a id="top"></a>
<a href="#top">Back to top</a>
</body>
</html>Learn more:
Related W3C validator issues
The name attribute is required for all input elements.
The value of the name attribute on an <iframe> should not start with an underscore (_).
Browsing context names that begin with an underscore are reserved keywords in HTML, like _blank, _self, _parent, and _top. Using these reserved names or any custom name starting with an underscore for the name attribute of an <iframe> can lead to unexpected behavior and is considered invalid HTML.
Here’s how to fix the issue:
Problematic Code
<iframe src="https://example.com" name="_example"></iframe>Solution
To resolve this issue, you should use a valid value for the name attribute that does not start with an underscore.
Corrected Code
<iframe src="https://example.com" name="example"></iframe>Steps:
- Identify the iframe element with the invalid name attribute value that starts with an underscore.
- Replace the name value with a valid identifier that does not start with _. Use letters, numbers, hyphens (-), and underscores (_) (but not at the beginning).
A <meta> tag has been found that is either malformed, or in a bad place within the document. Check its attributes and context.
For example, the following HTML contains a valid <meta> tag that is raising an issue because of bad context, caused by an <img> tag that shouldn’t be there:
<!DOCTYPE html>
<html lang="">
<head>
<title>Test</title>
<img src="photo.jpg" alt="A smiling cat" />
<meta name="description" content="Description of this page" />
</head>
<body>
<p>Some content</p>
</body>
</html>If we fix that document and move the <img> tag within the body, the issue raised about <meta> disappears because it’s now in a valid context:
<!DOCTYPE html>
<html lang="">
<head>
<title>Test</title>
<meta name="description" content="Description of this page" />
</head>
<body>
<p>Some content</p>
<img src="photo.jpg" alt="A smiling cat" />
</body>
</html>The itemscope attribute is a boolean attribute in HTML5, which means it does not take any values. Adding any value (such as true or false) will cause an error. When using boolean attributes, they should either be present or absent. If an attribute like itemscope is present, it is considered true.
Here’s how to correct the error:
Incorrect Usage:
<div itemscope="true">Correct Usage:
<div itemscope>Explanation:
- Simply including the itemscope attribute without any value is the correct way to use it.
- If you don’t want to use the itemscope attribute, just remove it from the tag.
Spaces are not permitted in the href value for phone links; the phone number must be a continuous string without spaces or slashes.
The href attribute of an anchor (<a>) element defines the link’s destination. For phone numbers, the proper URI scheme is tel:, not callto:. According to the HTML standard and the WHATWG Living Standard, the phone number should contain only digits and may use plus (+) or hyphen (-) characters for formatting, but it should not include spaces or slashes.
Incorrect HTML:
<a href="callto:07142/ 12 34 5">Call us</a>Correct HTML:
<a href="tel:0714212345">Call us</a>With country code and optional formatting:
<a href="tel:+49714212345">Call us</a>For best compatibility and validation, always use the tel: scheme and ensure the phone number string contains only allowed characters.
The value contact is not a valid option for the autocomplete attribute on an <input> element.
The dialog element does not require or permit a role="dialog" attribute according to HTML standards.
The <dialog> element has an implicit ARIA role of dialog, so adding role="dialog" is redundant and not valid per the specification. Instead, simply use the <dialog> element without an explicit role attribute.
Details:
According to the WHATWG HTML standard and ARIA specification, native <dialog> elements automatically have the correct role. Adding role="dialog" can cause HTML validation errors, as the validator interprets this as a misuse or redundancy.
Correct usage:
<dialog>
<p>This is a dialog box.</p>
<button>Close</button>
</dialog>Incorrect usage (causes validation error):
<dialog role="dialog">
<p>This is a dialog box.</p>
<button>Close</button>
</dialog>Removing the role="dialog" attribute resolves the W3C validation issue while maintaining accessibility.
The type dob is not valid for an input. If you want to build a date picker field, you can use the native HTML input elements with type date, datetime-local, or a generic text input decorated with JavaScript and CSS.
In HTML, the type attribute for the <input> element specifies the type of input control that is to be displayed. The type attribute can have values like text, password, email, date, etc. Using an unsupported or invalid value like dob (which presumably stands for “date of birth”) will cause this validation error.
Here’s an example of how you can correct this issue by using a supported type attribute value for the date of birth input:
<label for="dob">Date of Birth:</label>
<input type="date" id="dob" name="dob">In this corrected example, we’ve used the type="date" attribute value for the date of birth input. This is a valid type for handling dates in HTML forms. Replace the input type with a supported type according to the specific data you need to capture.
Alternatively you can use a JavaScript library to build a date picker on a generic text input. For example, the popular bootstrap-datepicker library will generate a date picker around a text input.
All HTML elements may have the hidden boolean attribute set. When specified on an element, it indicates that the element is not yet, or is no longer, relevant, so browsers won’t render it.
Boolean attributes don’t accept values, its presence represents the true value and its absence represents the false value.
<!-- This is invalid because the hidden attribute should not have a value set -->
<div hidden="false"></div>
<!-- The correct way to hide a div is like this -->
<div hidden>This will be hidden</div>
<!-- And to show the element, we just don't hide it -->
<div>This won't be hidden</div>Empty aria-controls attribute values are invalid; the attribute must reference the id of one or more elements.
The aria-controls attribute is used to indicate that the element controls the referenced element(s) by their id. According to the ARIA specification and W3C HTML standard, the attribute must contain at least one valid id value, and cannot be an empty string. Leaving aria-controls="" triggers a validation error.
Correct Usage:
- Assign an id to the element being controlled.
- Set the aria-controls attribute to match that id.
- Remove aria-controls entirely if not necessary.
Incorrect Example:
<a href="#" aria-controls="">Toggle</a>Corrected Example:
<div id="details">Some details...</div>
<a href="#" aria-controls="details">Toggle</a>If no element is being controlled:
<a href="#">Toggle</a>