HTML Checking for Large Sites

Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.

Your HTML markup contains an end tag for X, but there are nested open elements that need to be closed first. For example, <li><span>example</li> is invalid because you need to close the <span> tag before you close the <li>. This would be valid: <li><span>example</span></li>.

Related W3C validator issues