TYPO3 Core

empty link Tags: <a href="[url]" title="[title]">[nothing here]</a>

nested link tags <a href="[url]" title="[title]"><a[missing params]>[text here]</a></a>

missing link params: <a[missing params]>[text here]</a>,

wrong positioning of the tag: [text here]<a href="[url]" title="[title]">[nothing here]</a>,

plain text url: <a href="[url]" title="[title]">[nothing here]</a>[url again] and

split-up tags: <a href="[url]">[first part of the link text]</a><a href="[url]">[second part of the link text]</a><a href="[url]">[third part of the link text]</a>