Skip to main content

HTML Guide

Free site validation

Find out what web pages on your sites are affected by HTML issues.

Bad value “tel: X” for attribute “href” on element “a”: Illegal character in scheme data.

The href attribute on an <a> link contains an invalid character. 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>

Learn more:

Related W3C validator issues