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;
	display: box; display: flexbox;
	box-align: center; flex-align: center;
	box-pack: center; flex-pack: center;
}

div {
	padding: 1em 1.5em;
	margin: 1em auto;
	
	/* Make it pretty */
	background: slategray;
	text-align: center;
	border-radius: .3em;
	font: bold 100% sans-serif;
}

dabblet.html

<div contentEditable>OMG, I’m centered!</div>

settings.json

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