HTML Guide for b
An end tag </b> has been found in an incorrect place within the document, violating nesting rules. A common case is closing it before closing other nested tags, for example:
<!-- This line is incorrect as the <b> tag was closed before the nested <a> tag -->
<b><a href="#">link</b></a>
<!-- This line is OK as every end tag respects the nesting rules -->
<b><a href="#">link</a></b>