HTML + CSS only - three equal columns (33%~) with equal heights : <p>I'm having a huge issue and I suppose it may be not "doable", but I thought it would do no harm to ask.</p>

<p>I need three equal columns, with equal heights, but I don't know their heights, so this must be dynamic.</p>

<p>To make it even harder, each of these columns has different background colour.</p>

<p>Ideally the content would be vertically aligned, but that's not necessary.</p>
