HTML Guide
Free site validation
Find out what web pages on your sites are affected by HTML issues.
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:
Related W3C validator issues
The maxlength 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 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">The pattern attribute is only allowed on input whose type is email, password, search, tel, text or url. Check the type used, and consider changing to one of the allowed types to enable pattern client-side validation.
The pattern attribute is a handy way of adding client-side validation on HTML forms without resorting to JavaScript. Check out this article to learn more about Input Pattern.
The boolean required attribute can only be used with certain types of inputs. Check the input type is one of the allowed.
The required attribute, if present, indicates that the user must specify a value for the input before the owning form can be submitted.
The value contact is not a valid option for the autocomplete attribute on an <input> element.
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>An <a> element has been found with an invalid href attribute, containing more than one # adjacent character.
The # is used to separate the fragment part of an URI (typically used to indicate a section within a document). For example, this is a valid link to a URI containing a fragment:
<a href="https://example.com/faqs#pricing">pricing</a>The next example is invalid because it contains two adjacent # characters, so that the fragment part would be #pricing instead of pricing:
<a href="https://example.com/faqs##pricing">pricing</a>The href attribute of an <a> element contains an invalid character, that should be properly encoded as a URI percent-encoded character.
An illegal character has been found for the “href” attribute on the “link” element.
To fix this issue, find the “link” element in question and make sure that the “href” attribute contains a valid URL without any illegal characters.
Here’s some example HTML code of a link element:
<!DOCTYPE html>
<html>
<head>
<title>My Webpage</title>
<link rel="stylesheet" href="styles/main.css">
</head>
<body>
<h1>Welcome to my webpage!</h1>
<p>Here is some content...</p>
</body>
</html>In the above example, the link element has a valid href attribute value of styles/main.css. Make sure that your href attribute values don’t contain any illegal characters.
For rel="preload" and as="image" only, the imagesizes attribute is a sizes attribute that indicates to preload the appropriate resource used by an img element with corresponding values for its srcset and sizes attributes.