HTML Checking for Large Sites
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Bad value “” for attribute “href” on element “link”: Must be non-empty.
The href attribute on the link element must not be empty.
Related W3C validator issues
A <link> element has been found in an invalid body context. Check the attributes of the <link> element and ensure it’s not within the <body> section.
If the element is within the <head> section, it may have been interpreted as a body context depending on previous elements. For example, while this <link> element is valid per se and is in the <head> section, it is deemed invalid because the previous <img> element made the validator consider it a body context:
<!DOCTYPE html>
<html lang="">
<head>
<title>Test</title>
<img src="photo.jpg" alt="A smiling cat" />
<link rel="canonical" href="https://example.com/" />
</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>
<link rel="canonical" href="https://example.com/" />
</head>
<body>
<p>Some content</p>
<img src="photo.jpg" alt="A smiling cat" />
</body>
</html>
Learn more:
A <link> element that is using the preload value in the rel attribute is missing the as attribute, used to indicate the type of the resource.
The preload value of the <link> element’s rel attribute lets you declare fetch requests in the HTML’s <head>, specifying resources that your page will need very soon, which you want to start loading early in the page lifecycle, before browsers’ main rendering machinery kicks in. This ensures they are available earlier and are less likely to block the page’s render, improving performance.
The as attribute specifies the type of content being loaded by the <link>, which is necessary for request matching, application of correct content security policy, and setting of correct Accept request header.
Learn more:
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>
Learn more:
The href attribute of an <a> element contains an invalid character, that should be properly encoded as a URI percent-encoded character.
Learn more:
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An <iframe> element allows to embed an HTML document inside another HTML document, and its src attribute is indicated the source URL of the embedded web page. The src attribute is a required attribute, so it cannot be blank.
Example:
<iframe src="https://example.com/map.html"></iframe>
Learn more:
The href attribute on an a tag expects a valid URL, but only http:// was found.
<a> tags can be used to link to an email address using the mailto protocol in the href attribute. Ensure that there is no space in the email address.
<a href="mailto: liza@example.com">This is wrong as it contains an space</a>
<a href="mailto:liza@example.com">This is OK</a>
The href attribute on an <a> link contains a space character, which is not allowed. If you’re trying to link to a phone URL, review the href attribute to remove unallowed characters, as in this example:
<!-- Invalid as it contains a space character -->
<a href="tel: +123456789">call me</a>
<!-- Valid -->
<a href="tel:+123456789">call me</a>
Source:
Space characters are not allowed in href attributes. Instead, they should be converted to %20. In this example, the first line is invalid and the second is valid:
<a href="https://example.com#some term">invalid</a>
<a href="https://example.com#some%20term">valid</a>
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The href attribute on an element <a> contains a character that is not allowed, and should be encoded.
Some typical examples include the pipe character | that should be replaced by its encoded alternative %7C , and the left square bracket [ that needs to be encoded as %5B.
The href attribute on an <a> tag contains an space, which is not allowed. Consider replacing space characters with “%20”.
The at symbol (@) should be percent-encoded as %40 in order to include it at an href attribute.
The href attribute on an element <link> contains a character that is not allowed, and should be encoded.
Some typical examples include the pipe character | that should be replaced by its encoded alternative %7C , and the left square bracket [ that needs to be encoded as %5B.
The media attribute on a <link> element has not been recognized.
This attribute specified what media the linked resource is optimized for. As an example, the following will link a general stylesheet, and a specific one for printing:
<head>
<link rel="stylesheet" type="text/css" href="general.css">
<link rel="stylesheet" type="text/css" href="print.css" media="print">
</head>
Valid values for this attribute include:
-
all. Default, used for all media. -
print. Used for printers and print previews. -
screen. Used for computer, tablets or smartphone screens.
Learn more:
The value used to define the type of a link is not valid. You’re probably using a URL instead of a valid type.
Example of a valid type:
<link rel="icon" type="image/png" href="favicon.png">
Read more:
The <a> element requires either a href attribute, or a role attribute.
Learn more:
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