HTML Checking for Large Sites

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

End tag X seen, but there were open elements.

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