HTML Checking for Large Sites

<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>

Source:

• IETF: tel URI for Telephone Numbers

A < character has been found when an attribute was expected instead. Check the syntax of the affected tag, it’s probably malformed and a < character inside has been interpreted as an attribute.

For example, this code might cause this issue:

<!-- Malformed img tag -->
<img src="photo.jpg" alt="smiling cat" < />

<!-- Fixed img tag -->
<img src="photo.jpg" alt="smiling cat" />

Attributes for HTML elements must be defined like name="value". A common issue is missing the =, or repeating the " like in these examples:

<!-- Missing equal sign -->
<p name "value"></p>

<!-- Repeated quotes -->
<p name="value""></p>