End tag for element ... which is not open

Cause:

The validator found an end tag for the above element, but that element is not currently open. This is often caused by:

If this error occured in a script section of your document, you should probably read this FAQ entry.

Example:

Good<b>abc</b></b>
Good<b>abc</b>

This can also be due to bad javascript:

Gooddocument.write("</h1>");
Gooddocument.write("<\/h1>");

In such case, you need to escape the </ with "\".

Solution:

For a closing tag, remove the closing tag or add the missing opening tag before.

References: