&gt; &quot;Be conservative in what you do, be liberal in what you accept from others&quot;<p>Wikipedia has an example of a tag soup <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Tag_soup" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Tag_soup</a> which is probably poster child example of this law:<p>&lt;p&gt;This is a malformed fragment of &lt;em&gt;HTML.&lt;&#x2F;p&gt;&lt;&#x2F;em&gt;<p>What do we do here? Do we do what browsers have historically done? Or do we throw our hands up in the air when we see malformed tags?