The first commented line is your dabblet’s title
{"view":"split-vertical","fontsize":"100","seethrough":"","prefixfree":"1","page":"css"}// alert('Hello world!');
<!-- content to be placed inside <body>…</body> -->
<div>
<h1>this is a test</h1>
<p>this is something else</p>
</div>
/**
 * The first commented line is your dabblet’s title
 */
div{
	width: 500px; 
	height:800px;
	position: relative;
	margin: 150px 0 0 250px;
	z-index: 51;
}
div:after{
	content: ' ';
	display: block;
	position: absolute;
	background: yellow; 
	width: 500px; 
	height:800px;
	z-index: 0;
	margin: -150px 0;
	border-radius:100px;
	transform: rotate(-60deg);
}