Edit in JSFiddle

$(".fancybox").fancybox({
    openEffect  : 'none',
    closeEffect : 'none',
    afterLoad   : function() {
        this.inner.prepend( '<h1>1. My custom title</h1>' );
        this.content = '<h1>2. My custom title</h1>' + this.content.html();
    }
});

<a href="#test" class="fancybox">Open</a>

<div id="test" style="display:none;width:300px;">
<p>
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque blandit, mi sed sollicitudin hendrerit, elit elit tristique velit, ut sagittis urna dolor non metus. Fusce viverra lacus sit amet urna porttitor eu mollis massa hendrerit.
</p>
</div>