Vertical centering with Flexbox + margin fallback

dabblet.css

/**
 * Vertical centering with Flexbox + margin fallback
 * Lea Verou & David Storey
 */

html, body { height: 100%; }

body {
	width: 100%; /* needed for FF */
	margin: 0;

}

#wrapper {
	/* Make it pretty */
	background: slategray;
	text-align: center;
	border-radius: .3em;
	color: #405060;
	font: bold 150% sans-serif;
	text-shadow: 0 2px 1px hsla(0,0%,100%,.2);
}
#sidebar {
	/* Flexbox hawtness */
	display: box; 
	display: flexbox;
	padding: 1em 1.5em;
	background: #bbb;
	width: 30%;

}

#main {
	padding: 1em 1.5em;
	display: box; display: flexbox;
	width: 70%;
	}

dabblet.html

<div id="wrapper">
 <div id="main">Main content</div>
 <div id="sidebar">Sidebar</div>
</div>

settings.json

{"view":"split-vertical","fontsize":"100","seethrough":"","prefixfree":"1","page":"css"}