HTML Checking for Large Sites

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.

The href attribute on the link element must not be empty.

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>

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 contains an space, which is not allowed. Consider replacing space characters with “%20”.

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 at symbol (@) should be percent-encoded as %40 in order to include it at an href attribute.