HTML Checking for Large Sites

The href attribute of an <a> element contains an invalid character, that should be properly encoded as a URI percent-encoded character.

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>

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 <a> element requires either a href attribute, or a role attribute.

An a element with an href attribute provides a link to a resource, so adding the link role to it is redundant.

When not using semantic HTML for its intended purpose, interactive features must be re-implemented. For example, when role="link" is added to an element, the tab key should enable giving focus to the link and the enter key should execute the link when focused.

A button element, or an element with the role=button attribute, is not allowed to be nested inside an <a> element.

An <a> element cannot contain a descendant element with the attribute tabindex.

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 on the link element must not be empty.