HTML Guide for href
An href attribute on an a element contains an invalid URL that has space characters in the domain.
The domain in a URL cannot contain space characters, for example the following are invalid:
<a href="http://my domain.com">link</a>
<a href="http://my%20domain.com">link</a>
The at symbol (@) should be percent-encoded as %40 in order to include it at an href attribute.
An href attribute with the value http:// is not a valid URL because the host section is missing.
The href attribute in the area element must contain a valid URL. A URL requires a scheme (http or https), followed by ://, and then a valid host (such as example.com). The value http:// lacks a host, making it invalid according to URL standards and resulting in a validation error. If you don’t want the area to navigate anywhere, you can use href="#" for a placeholder or omit the href attribute entirely. To link to an actual location, provide the complete URL, including the host.
Invalid example:
<map name="myMap">
<area shape="rect" coords="30,23,183,191" href="http://" alt="" >
</map>
Valid example with a real host:
<map name="myMap">
<area shape="rect" coords="30,23,183,191" href="http://example.com/" alt="" >
</map>
Valid example with a placeholder, no navigation:
<map name="myMap">
<area shape="rect" coords="30,23,183,191" href="#" alt="" >
</map>
Replace http:// with a full URL or a suitable placeholder as needed for your application.
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 <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.