HTML Checking for Large Sites

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>

Learn more:

• HTML Living Standard: Browsing context names

<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 accept attribute may be specified to provide browsers with a hint of what file types will be accepted on an <input> element. It expects a comma-separated list of allowed file types. Refer to the list of media types to check the accepted tokens. In this example, the first line is invalid while the second is valid:

<input name='file' type='file' accept='doc, docx, pdf' />

<input name='file' type='file' accept='text/doc, text/docx, application/pdf' />

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/?s=some term">invalid</a>

<a href="https://example.com/?s=some%20term">valid</a>

Space characters are not allowed in src attributes. Instead, they should be converted to %20. In this example, the first line is invalid and the second is valid:

<img src="https://example.com/?s=some term" alt="description" />

<img src="https://example.com/?s=some%20term" alt="description" />

The src attribute on an <img> tag is not allowed to contain space characters. You should replace them with “%20“.

An HTML tag could not be parsed, most probably because of a typo.

An </a> end tag has been found to violate nesting rules. <a> tags can’t include other <a> tags inside. Most probable cause is an unclosed <a> tag, like in this example:

<a href="one.html">Page 1

<a href="two.html">Page 2</a>

The document has been declared to use a windows-1251 charset but the actual contents seems to be utf-8. You should update the charset to that like in this example:

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">

An <a> tag can’t include other <a> tags inside. Most probable cause is an unclosed <a> tag, like in this example:

<a href="one.html">Page 1

<a href="two.html">Page 2</a>

Read about Normalization in HTML and CSS.

A <label> tag can’t be used inside an <a> tag. Consider using other tags like <span>.