HTML Validation

Bad value “X” for attribute “rel” on element “Y”: The string “X” is not an absolute URL.

About This HTML Issue

The rel attribute defines the relationship between a linked resource and the current document. Valid on <link>, <a>, <area>, and <form>, the supported values depend on the element on which the attribute is found.

Here’s an example of using the rel attribute to link a document to a CSS stylesheet:

<link rel="stylesheet" href="default.css" />

Here’s an example os using the rel attribute to tell search engine spiders to ignore the link relationship with another document:

<a href="https://example.com" rel="nofollow">more info</a>

Learn more:

→ MDN - rel

Last reviewed: March 21, 2023

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Related W3C Validator Issues (73)

Bad value “"true"” for attribute “aria-hidden” on element “div”.

The attribute aria-hidden must have a value of "true" (without extra quotes) or "false", not "\"true\"" (with double quotes inside the value).

The aria-hidden attribute is used to indicate whether an element and its children should be accessible to assistive technologies (like screen readers). Valid values are the strings "true" or "false" (without embedded quotation marks). Using extra quotation marks causes the validator to flag a bad value because the attribute’s value is interpreted literally.

Incorrect Example:

<div aria-hidden='"true"'>This is hidden from assistive tech</div>

Correct Example:

<div aria-hidden="true">This is hidden from assistive tech</div>

<div aria-hidden="false">This is visible to assistive tech</div>

Remove any extra quotation marks around your attribute value to resolve the error.

A “link” element with an “as” attribute must have a “rel” attribute that contains the value “preload” or the value “modulepreload”.

The error message indicates that the <link> element contains an as attribute, but its rel attribute does not hold the correct value. According to the HTML specification, when using the as attribute, the rel attribute must be set to "preload" or "modulepreload".

Explanation

The as attribute is used to specify the type of content being loaded, which helps the browser to handle it appropriately. To preload resources, you need to specify the rel attribute with the value "preload" (for general resources) or "modulepreload" (specifically for JavaScript modules).

Example with preload:

If you are preloading a stylesheet, the rel attribute should be set to "preload":

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Correct Usage of Link with as Attribute</title>
    <link rel="preload" href="styles.css" as="style">
</head>
<body>
    <p>Hello, World!</p>
</body>
</html>

Example with modulepreload:

If you are preloading a JavaScript module, the rel attribute should be set to "modulepreload":

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Correct Usage of Link with Modulepreload</title>
    <link rel="modulepreload" href="script.js" as="script">
</head>
<body>
    <p>Hello, World!</p>
</body>
</html>

Attribute “maxlength” is only allowed when the input type is “email”, “password”, “search”, “tel”, “text”, or “url”.

Attribute “minlength” is only allowed when the input type is “email”, “password”, “search”, “tel”, “text”, or “url”.

The minlength attribute can be used on an input element to define a client-side validation for the maximum length allowed on an input without resorting to JavaScript.

This attribute is only allowed on elements of type email, password, search, tel, text, or url.

The minlength attribute defines the minimum number of characters (as UTF-16 code units) the user can enter into an <input> or <textarea>. This must be an integer value 0 or higher. If no minlength is specified, or an invalid value is specified, the input has no minimum length. This value must be less than or equal to the value of maxlength, otherwise the value will never be valid, as it is impossible to meet both criteria.

Here’s an example:

<label for="name">Enter your name (max 25 characters)</label>
<input type="text" minlength="25" id="name">

Attribute “pattern” is only allowed when the input type is “email”, “password”, “search”, “tel”, “text”, or “url”.

Attribute “required” is only allowed when the input type is “checkbox”, “date”, “datetime-local”, “email”, “file”, “month”, “number”, “password”, “radio”, “search”, “tel”, “text”, “time”, “url”, or “week”.

Bad value “0” for attribute “aria-rowspan” on element “div”: Zero is not a positive integer.

According to the ARIA specification, the attribute aria-rowspan is expected to have a positive integer value. A positive integer is a whole number greater than zero.

Explanation

aria-rowspan: This attribute is used in ARIA-enabled tables to indicate how many rows a cell should span within its row group. It is often used in elements like gridcell or rowheader within roles that imply grid-like structures, such as grid or treegrid.

Example of Incorrect Usage

<div role="gridcell" aria-rowspan="0">Content</div>

In this example, aria-rowspan is set to "0", which is not a valid positive integer.

Correct Usage

To resolve the issue, you should specify a positive integer. For example, if the cell should span one row, you can write:

<div role="gridcell" aria-rowspan="1">Content</div>

If the cell should span multiple rows, adjust the number accordingly:

<div role="gridcell" aria-rowspan="2">Content</div>

Considerations

Make sure the role attribute is correctly associated with an element that can logically have a row and grid structure, such as gridcell.
Ensure that the aria-rowspan value aligns with the structure of your grid or table, representing the actual number of rows that the element is spanning.

Bad value (true|false) for attribute “itemscope” on element “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.

Bad value “callto:X” for attribute “href” on element “a”: Illegal character in scheme data: space is not allowed.

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.

Bad value “contact” for attribute “autocomplete” on element “input”: The string “contact” is not a valid autofill field name.

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