<p>As a general principle, the first thing to do is consider the possibility that you're mistaken. If there's already comments there, check to see what the discussion says and what may already have been done about it</p>

<p>Then:</p>

<ul>
<li><p>Try commenting about the issue first; perhaps the poster can be induced to fix it themselves.</p></li>
<li><p>Consider also posting a correct answer where you refer to the mistaken one.</p></li>
</ul>

<p>Actually correcting someone else's answer would normally be limited to minor fixes (downvotes and or comments are the usual way to indicate disagreement), but I can see the increased desire to deal with it when there's a popular but potentially misleading answer that novices might accept uncritically.</p>
