<a href="http://corknut.org"><ins><div> div contents go here </div></ins></a>
Because while <div> isn't allowed inside <a>, it is allowed inside <ins>, which in turn is allowed inside <a>. And it validates! How ridiculous.
Then make sure the div's style uses
cursor: hand;so that it looks like a link to the visitor.
(Thanks to okb for figuring this out for me.)
Edit: Okay, better solution: <span> is allowed inside an <a>, and with the
display: block;style it works the same as a <div>. So that's what I ended up using.