HTML Guide
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The value used in the target property of an <a> element has been identified as a keyword because it starts with an underscore _, but it’s not a valid keyword.
Values starting with an underscore for the target property are used for reserved keywords like _blank, _self, _parent or _top.
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Related W3C validator issues
The target attribute on <a> elements can’t be blank.
This attribute defines the browsing context for links, that is, where should the linked documents be opened. This was used extensively on the now deprecated <frame> element, so you could give the name of the frame to open the document in, but is now more used to force links to open in a separate tab or window using target="_blank". Another option is using a name, so the new browsing context can be referred to on subsequent clicks on links with the same target.
For example, this will force the links to open on a new tab:
<a href="https://example.com" target="_blank">will open a blank tab</a>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.
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 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>Hash (#) characters can be used in an href attribute to link to a specific part of a document.
For example, if we have this page with several sections, each of them marked with an ID:
<h1>Frequently Asked Questions</h1>
<h2 id="pricing">Pricing</h2>
<p>All about pricing...</p>
<h2 id="terms">Terms</h2>
<p>You can find our terms at...</p>
<h2 id="guarantee">Guarantee</h2>
<p>We offer a guarantee...</p>You can link to a specific part of that document, for example if this page URL is /faqs and you want to link to the Guarantee section you could use:
<a href="/faqs#guarantee">Guarantee</a>Or, if you’re linking from inside the same document, for example in a table of contents, you could just use:
<a href="#guarantee">Guarantee</a>As there can only be one fragment in an URL, the # character should only be used once. The following would be an invalid href:
<a href="/faqs#guarantee#pricing">Bad</a>If needed, the # could be encoded as %23.
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”.
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>