title: When to use <strong>, <em> or <mark>?
body: <p>Sorry if this is sounding fussy but I'm about to produce a whole lot of HTML 5 and I was hoping someone out there had come up with some clear rules for when to use the &lt;em&gt;, &lt;strong&gt; and &lt;mark&gt; tags. The spec suggests some subtle differences but I keep finding myself asking whether I want the text bolded, italic or yellow high-lighted, which makes me think I should be using CSS instead. (And sometimes I wonder why I even bother when I could just as easily write "Cats are NOT dogs.")</p>