Iframe on fancybox

Is there a way so I can open an Iframe (contact form or other html) inside the Fancybox?!

I already tried using this(extracted from the Fancybox site) with no success.
<a href="/demo/iframe.html">Iframe</a>

And I saw that when you calls an image with Fancybox it uses “class=openfancybox-image”, different than the original sentence from Fancybox site “class=”fancybox”, can you explain me a little?!