A fun exercise brought to you by HTeuMeuLeu: the marcolago's solution

dabblet.css

/**
* A fun exercise brought to you by HTeuMeuLeu: the marcolago's solution
* http://www.hteumeuleu.fr
* http://www.hteumeuleu.fr/a-css-brain-teaser/
* http://www.twitter.com/HTeuMeuLeu
*/

body { padding:50px; background:#2fa7ca; }
h1 { font:bold 36px sans-serif; letter-spacing:-1px; color:#000; }

header {
	width: 480px;
}

h1 {
	display: inline;
	background-color: #ffffff;
	line-height: 1.42em;
	box-shadow: -20px 0px 0px 10px #ffffff, 20px 0px 0px 10px #ffffff;
}

dabblet.html

<header>
	<h1>Some dynamic HTML text on several lines with a background that suits well and some margins around it.</h1>
</header>

settings.json

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